Good, good...!
...and it's very good actually!
Art is very well placed, it has a cartoon style, with lots of personality. Cut-scenes use stills a-la comic book, but with style (it's funny that I played X3 before TMNT, and the 1st also uses stills, but... so, so much worse...!)!
Characters movent are fluid, in a sense like they actually seem to weight - the way that they wave on the poles for instance, good stuff.
Sound is fair, sometimes well placed, sometimes dull. Average.
Gameplay, control-wise, and level-design is well above average. It's polished enough to deliver a few fun-hours. Combos, plot, and all surrounding stuff goes well together. Allways fun to look at, and witn simple funny lines. It's also a family friendly title, it has almost no sense of violence - even the fighting sequences deliveres no idea of violent behavior.
On the down side - one should be able to controll the camera, and co-op would be brilliant.
Another title that goes proudly to the collection shelve.