I didn't really like the actors staring at the cameras and all the comments about the series itself (like Rose mentioning the pilot). I was pretty shocked when the piano killed "Charlie", but maybe because I was expecting him to appear (actually I thought I had spoiled myself a little reading the last line of the subtitle file, the one that said Winning).
Read the vanity card too and I think it would have been a better idea going with the one Charlie supposedly proposed, too bad there won't be any The Harpers.
I actually liked the Friends finale; The alternate HIMYM finale is the real one for me; I LOVE the Cheers finale; and the only reason I don't like the Seinfeld finale is because it was full of inaccuracies (just two off the top of my head: Jerry was always trying to help Babu, it's not his fault the later couldn't see his intentions; and Susan was actually the one who made the bubble explode - The Bubble Boy was choking poor George!.)