The first season was very impressive most of the time, especially the episode "Rookies" which was all about the Troopers. I still hate the fact that the show exists, and was transferred for a theater release. I hate the idea that they created the character of Ahsoka, not only because she is annoying, but she makes no sense at all, completely shoehorned in there. Also, Matt Lanter is not a very good Anakin.
The second season was split about 50/50 for me. Too many lame episodes that focus on things like the spider guy (Trench), the Zillo beast, and they entered too much into the EU realm for my liking by including holocrons and the kaiburr crystal. Boba Fett's arc was terrible, which is unfortunate because I was really looking forward to it. I don't know why they decided to make him some innocent young boy. In most ways his arc on the show put him a few steps back from where he was in Episode II.
The third season looks as though it is completely jumping the shark, though I will give it a shot. Cad Bane originally seemed interesting because he had to come up with creative ways to fight the Jedi, but now they're giving him a lightsaber, which is beyond stupid. Also they're introducing the Nightsisters (another really bad EU creation) and, because of the genius writers on the show, Darth Maul's brother.
Seriously. He's Darth Maul but yellow and with longer horns. And his name is Savage Oppress. Seriously.
I'm glad George draws the line between his story and "everything else", but some stuff I just wish he wouldn't allow to be made.