For me, the second half of season 2 is too little, too late really. There's not enough attachment to the characters actually built up in the first 1.5 seasons to make the ending feel as earned as it should have been. It drew a little too much upon sentimental memories I had of graduating from high school myself, which isn't good enough. Anything can cheaply draw on common emotional experiences shared by much of the populace in order to get a reaction. Aria has to build new gondola-related feelings from the ground up, dammit, I've never even been in a gondola!
(Plus, they're all going to the same college next year, aren't they? The only one who has anything to feel sad about is Ui, and she's kind of a freak. And Azusa, but nobody cares about Azusa.)