Honestly, I like FF8, and in the past have written lengthy posts dissecting the characters, including Squall and Rinoa, and explaining why they behave the way they do. However, that was a long time ago and I don't feel like repeating myself.

THAT SAID, I believe it is theoretically possible, given a slew of motivations, for Squall to have done a 180 in the game. Given his crummy life and the issues he needs to go through - yet his expressed desire for change which occurs in his dreams, it is plausible. However, the problem is, we DON'T SEE IT IN THE GAME. As a graduate playwright and a screenwriter, I can give my professional opinion, that in FF8 Square did the following:
1. They came up with some great characters with interesting, complex backgrounds.
2. They came up with a great ending in which those characters had grown and changed.
3. They completly failed to evolve the characters from point A to point B in a logical or belivable manner.

Squall and Rinoa are a great idea for a couple - their differing backgrounds and personal issues should have a great deal of effect on one another, but we don't see it. We discover these things about the characters, some gameplay happens, and suddenly the characters are acting completely differently, with no real evidence of emotional change. Square really needed to work in Squall's softening towards Rinoa much more gradually - perhaps he doesn't act different in front of her, but keeps looking when she leaves the room, or argues with himself. Something. But they didn't, not really.

And thus, we have a lot of people who are irritated by the storyline and characters for just that reason. And although that didn't wreck the game for me (perhaps because I've rewritten it a bit in my head - lol), it really annoys others, and I don't blame them for that.