For the most part I found the series quite enjoyable, which was especially nice since my experiences with other comedies really haven't been.
The animation was nothing special and a bit bland compared to many of the more recent shows. While being far from outstanding it wasn't bad either. The animation was simple and worked well enough as to not detract from the show. In general this is true for most of the elements of the show.
As far as the actual comedy goes, I found Sayonara Zetsubou Sensei funnier than the other comedies I've watched, eliciting laughs and snickers throughout its duration. However, while certainly amusing it was far from hilarious and failed to deliver any real side-splitting moments. Additionally, as I progressed through Sayonara Zetsubou Sensei, I found that some of the later episodes were a bit lacking. I found that instead of focusing on comedy it de-railed a few times to make a point. While I'm not specifically against that, I found that the point that was trying to be made was very obvious and could be gleamed within the first 5 minutes of the episode. Despite this it yet continued to drag on for half the episode, (perhaps that was supposed to be funny) leaving me a bit bored.
For the most part I found that I quite enjoyed Sayonara Zetsubou Sensei despite no specific elements of the series standing out and the comedy spotty at times. Hopefully, there will be some refinement in the following series and it can regain what it was that made the first few episodes particularly enjoyable.