The first season of Clone Wars was pretty bad - too many Anakin-Ashoka-Obiwan episodes. Ashoka ruins the character dynamic there; she's tolerable when she's just with Anakin, but when with both of them, the repetition is quite annoying. There was also a ton of Battle Droid humor, which got old, fast, especially since unlike Jar-Jar, who's a sentient being, Battle Droids are robots, so the idea of them making unintentionally smartass remarks and such is nonsensical unless programmed as such.
I don't think I saw any of Season 2, not even the Zillo Beast arc, but Seasons 3 and 4, excluding a few choice moments (the Mortis trilogy, Even Piell's last scene, Anakin's angst when Ashoka disappears) have generally been big improvements. The overall Nightsisters arc between both seasons in particular, even if it has some weak dialogue, has a great over-arching story going on, even if the Bounty one made me facepalm for most of it's ending.
Also, I think the series works very strongly when they involve non-traditional elements. Chewbacca, Tarkin, and Darth Maul have been treated rather respectfully, and Even Piell was doing quite well until he received quite a lame death.
I hate to say it though, I do look forward to Ashoka and Rex's "deaths". Considering they wrote out Piell to explain his pseudo-absence in ROTS, I'm quite sure they'll kill them both off. James Arnold Taylor, Obi-Wan's voice actor, even hinted towards Ashoka's death.
Of course, they might be cheap and let her survive Order 66 somehow.