I simply don't get this hate for Lady Gaga. It's one thing to not enjoy the music. It's another to automatically put down an episode that hasn't even aired! Who knows how it'll turn out?
Like it or hate it, the fact of the matter is that she's commercially successful, and appeals to a wide audience. That isn't even up for debate.
Look at N'Sync. They were the boy band flavor of their time, and it was enough to generate a very amusing, if somewhat surreal episode based around them.
Personally, I'm looking forward to this finale.