Elena becoming a vamp and them picking the worst of both worlds by keeping Klaus around in Tyler's body (they didn't have the guts to kill Klaus, but JM was just about the only thing that made Klaus likable).

I'm working on a way to get out of the first and justify the second by having Klaus able to keep Elena human and you know he'd want to do it.

Then there's the Triangle (always the Triangle) issues and the underuse of Elijah.

All told I'm still not very happy.