I have no problem with this series being non-canon. As awesome as much of it is, none of the Jedi abilities jibe with the rest of the Star Wars material. Similarly, Grievous is exponentially cooler in that series than in any other incarnation.
I consider it canon for the simple fact that as far as I remember there isn't anything that really contradicts it outside of, as I said in the Star Wars OT, Grievous' cough.