When I first saw the movie, I was a bit hesitant; Lucas using the EU? Anakin having a Padawan? I wasn't too impressed by it, and left the series alone for a bit. Then I saw the first episode. Damn. Yoda kicking ass in a lushly detailed world. And then I decided to take the series more seriously.
Clone Wars manages to draw on the varied history of the EU to craft a new saga in the series. Despite being a kids show, it has a mix of action, adventure, and even dialogue that elevates it above the standard slop that passes for children's television. Many of the episodes manage to pack well-made battles and exciting stories into the constraint of 20 minutes (such as the Ryloth Arc, Landing Point at Rain, Malevolence Arc), and the occasional attempt to branch out leads to fairly good results (Trespass, Mandalore Arc). Beyond that, the CG has begun to shine, especially as the series moves forward.
Of course, the series has had a few less then stellar episodes (Zilo Beast), and about one bad episode per season (Corruption). Generally, those episodes either try to be radically different from Star Wars or suffer from bad writing. Still, the amount of bad episodes is fairly low, and not enough to dissuade me.
The question of EU canon and the show is often brought up. As a dedicated EU fan who's read most of the series, I suggest taking a relaxed view, and remember that Lucas has the final say. Does it really matter when Anakin got his scar, that Hutts aren't parthenogenic, or if Kenobi liked someone? And for the continued naysayers, I ask that you wait until the series ends and let the professional ret-conners work it out; if Jedi Prince, Fetts convoluted backstory, and even Sith history can be fitted in, this series can be as well.
My final opinion? I can understand why people don't like it; it's fresh EU in a chapter that was thought closed, and Ahsoka doesn't sit well. But despite these things, it shows a surprising amount of detail and focus, and is still
better then the shit the EU has churned out for decades (Jedi Academy Trilogy, Callista Trilogy, Black Fleet Crisis, Corellian Trilogy, ect ect). Give it a shot, and if you hate it, you'll have lost little time.