I agree, the "finale" was out of place and terrible, but what really makes me mad is that there's no way Kelso's leaving could've been the end and someone just mixed up some tapes somewhere, since last week's episode has Cox filling in for Kelso while they look for a replacement.
Having said that, I did kinda like that this season didn't end with a wrap-up, everyone's happy sort of ending, and instead just on a melancholy note (literally).