Just watched pilot. Veeery hit and miss. The writing is solid. I'll give them that, if anything else, there are some truly witty remarks and genuine humor in this series for anyone of any age to enjoy. Its just everything else surrounding it that kinda sucks. The middling plots are the weakest point, there isn't much substance to what they're doing and why they're doing it, no real direction yet. Also, some of the CG designs for background and BG characters are god fucking awful, the badger thing in the pilot looked awful in comparison to the main cast and the environments are lacking. In terms of character art and animation, I like the designs and I think it looks super polished. The anims lag behind though, the movements look eh.
But as I said, the humor is there, and its genuine (some times). Whoever is in charge of writing dialogue should be given a raise because its one of the few things good about the series thus far. Of course though, a series can change a lot and grow quite a bit in its first season, so I'll tough it out and check up on it again in a few months to see if its gotten any better.
Overall: 6/10, not terrible. Sonic fans should give it a go and others should still at least try it out (hell, I did).