I think he'd be COMPLETELY different as a partner, than during the rest of his life's activities: He is someone who truly and completely lives for love and only for love - every action he does is for Lily, that's the only meaning any action could possibly have for him if it has any meaning at all. He was like that towards Lily both when she was alive and then when she was dead.

When it comes to love, he's not the Snape we know from classes and so on. He's completely romantic and tender towards the one he loves, as we can see it in his many Lily-related memories (even when they quarrel, you can feel this deep emotion he holds for her and this huge vulnerability he's got as the gifted and emotionally profound person he is, and this sadness because of love). (And it's also out of love that he becomes bitter and a bullying man, because love has such a strong impact on him. His every attitude comes from love. That's what makes him so different from other men and so special - cos normally you don't base all your actions and attitudes of your every day life on love, it doesn't normally determine every situation of your daily life. Normally you're able to act independently from love in your every day life, you're able to act normally, if you're a responsible adult. Snape, however, is downright capable of such insanity. He's completely gorgeous. (even if his behaviour is downright childish when he makes innocent people like Harry pay for his bitterness). But this childish, unconditioned love is what makes us love him so much I think, however unfair he was.

James, on the other hand, oh no, honestly, James, he's just so obsessed with himself, I don't think you could EVER get from him what Snape is capable of and willing to give someone he loves - that is to say: Snape just completely gives himself, he completely hands himself over to the one he loves (he even hands himself over to Lily via DD), his love is absolute.

James is just too busy with himself and the image he wants to create of himself, to be able to conentrate that intensively on a human being other than himself. He's compeltely loathable, what a nutter. He never had Snape's both intellectual and emotional profoundness, his capacity of very deep feelings - James is just so superficial, in my opinion.

Then there are what I call the "Dude Looks Like a lady" quotes - there are the trolls in tutu's, the gnome in a tutu, Crabbe and Goyle disquised as all sorts of girls and Hagrid wearing a pink apron called, in the books a "flowery pinny" - what did all that hint at if not Love Potion?

Is it a sign that JKR was considering Love Potion and then changed her mind or were they hints at something else?

"Also remember Harry had that piece of soul within him. Could only Voldy hit him with the AK, to get rid of it?"

Apparently.

From Chapter 33 of DH -
(SS): "So the boy ... the boy must die?"
(DD): "And Voldemort himself must do it, Severus. That is essential."

Lily was just his "love", because she was the only girl that was nice to him, even though she was nice to everyone (Except Voldy ) But, in the end, he blew his chance by picking the Death Eater friends. What, did he think that she, an Order of the Phoenix member, may too, become a Death Eater?

No just about anyone can be imperiused, and it takes real strength of mind to beat it. Harry did learn how to beat it but we aren't told that anyone else in his year did. Crouch Jr. and Sr. both at least partially beat the curse, but in both cases it took them months or even years.

Snape didn't give himself completely to Lily. He chose Voldemort over Lily.

Lily didn't choose the arrogant toerag James Potter over Snape. She chose the reformed character James who was kind and loyal and funny about a year after Snape had rejected her in favour of his death eater friends.

And as for Snape's superior intellect. This goes against what we're told of both James and Sirius being the best wizards in the school in their Hogwarts years.
And his "emotinal profoundness"? He was just obsessed with Lily. He never even bothered to get to know her properly, or else he would have known she wouldn't accept his obsession with the dark arts. He loved the idea of Lily. An imagined, idealised Lily. Not the real Lily.

Do you remember who said that? About James and Sirius being the best wizards at Hogwarts in their time? Because I tend to think that Snape was just as smart. He was inventing spells, for one thing, which we've never seen anybody else in the series do. And his Potions talent was just astounding.

J.K. said that the idea of Snape being in love with you was "horrible," and I tend to agree, despite my moniker.

For one thing, he'd probably be so possessive, you could say goodbye to all your friends...especially your male friends. I agree with The Sorting Hat -- that "greedy" look he gives Lily says it all: "creepy stalker!"

He'd probably also be the kind of boyfriend who calls you 20 times in a row, and leaves you 20 different voicemails if you don't pick up. Because if you don't pick up the phone, you must be cheating on him.

Then there's the fact that you can't take him anywhere. Without worrying about him terrorizing little children, or cursing any male waiter who came near you, I mean. ("I told you, we don't want any more bread! Sectumsempra!")

And can you imagine the head games involved in having a boyfriend who can read minds? ("You are thinking of a number between 1 and 10..." / "Stop it, Sev, I don't want to play anymore!" / "Six." / <sigh> "Yes, six.")

And then, if that weren't enough, there's the whole "let's-see-how-dirty-my-hair-can-get-before-somebody-actually-says-something-to-me-about-it" thing.

And yet...I haven't been able to stop thinking about him for 6 years straight...

@Wendall: Of course, yours is the healthy, perfectly sane, reasonable, adult, well-organized-minded and thouroughly rightful take on Snape's love-ways. There's no questioning this!

When he dedicated himself to Voldemort's bidding, this was not because of Voldemort, but because he thought that this would really really impress Lily if he were to become a true DE and when she'd see that at last. Remember that he really lacked what James had: heroism, glory, attention, coolness, adventureness, courage... He stupidly thought that by making himself become a real DE, that this would mean getting or proving to have all those things. He sickly persuaded himself that once Lily would really see him going on dangerous adventures with the DEs, she'd find that really cool. He didn't want to admit to himself that, again, what he was doing and being like was wrong and disgusting and uncool, when he thought he'd finally found himself something very cool to do and be like. (Remember that at that moment, nobody yet knew what Voldemort was going to become and do in due course. - It was more of a gothic gang-like thing then, at least surely in the eyes of many young people, who didn't know what they'd really signed up for then. Remember Snape's opening-of-the-eyes when Voldemort started hunting down the Potters.)
So he stupidly chose Voldemort because of Lily, he never chose Voldemort because of Voldemort.

And as for the intelligence-discussion: Personally, to judge someone's intellect, I don't normally rely on who is commonly "said" to be the best ones, because remember, for one thing, James and Sirius were great boasters (unlike Snape, who was shy and turned inwards), so they would easily count very quickly as the best ones, and also: they were admired by many because of their coolness, when Snape wasn't, so people wouldn't really be drawn to talk well about Snape or about something about him (if they noticed him at all).

Secondly, I don't really take school-marks and teacher-sayings into account that much if I am to judge someone's intellect (although Snape surely had brilliant marks just as J&S). For me, J%S were never intellectuals however intelligent they were. These are not the same things. Snape was an intellectual. James was really really intelligent, but so superficial nevertheless. Also, emotionally, he could never have immersed himself so deeply (however sick that was in Snape's case) into love or obsession as Snape could (and that's exactly what I love about Snape and what so bores me about James). I'm not thinking about being sick or healthy right now (that's, of course, another, and very important, question) - but now I'm talking about what passionates (Snape) and what bores me (James).

And besides, James never stopped bullying Snape - he just didn't do it in front of Lily any more, as I think Lupin is pointing out. Both James and Snape are tactless people, each of them out of different reasons.

Oh, come on, you're not kidding yourselves into believing that James was becoming all social, altruistic (and not only towards people he considered to be cool), empathic, calm, serious, reasonable, understanding, sensitive and so on later on! I mean, if you grow up being made a little pampered prince like that and then have the same status in school as well, how can you suddenly wake up one morning being totally different? There'd have to be a huge event in your life to be able to change you that much! (Lily apparently wasn't enough an event like this, as he never quit bullying Snape and never apologized for it).
You're defending James coming up with this big and true changing of character-story, but in Snape's case, you don't see the change there definitely has been in his case, when in James's, we don't really have evidence at all about how he was really like from his seventh year on.