The point isn't that there wasn't developement, it's that it happened too rapidly. The point was that he thought of Rinoa as a hindrance and an annoyance, and the second she goes comotose, he's completely and totally head over heels in love with her. It was poorly done.
I think the point they were trying to get across is "you never know what you've got until you've lost it". He thought he'd lost Rin, and suddenly realised what he had (not just her but friends and other Good Things) and how ignorant he was of it. That's what I think anyway

Oh, and Jolts, fix your sig :P Having to scroll left and right all the time to read your posts is really annoying! kkthxla~