Overall, very well done with this. The concept seems to be executed very well, and the attention to anatomy and motion is great. I do think that the motion of the hair and tail could be made a bit more dynamic, since at the moment they feel a bit stiff. Also, you could possibly smooth out the transition between frames and try to emphasize the slinky/loping movement of the feline body. Cats are very springy when they move, especially when moving quickly, and I think you could do a lot to bring this into the piece. It might also be interesting if you cold add some of the springy/slinky feline feel to the human torso, adding a bit of bend to it to tie it even more to the lower body. I understand that this could be tricky with a six-limbed creature, but I think you could pull it off.
First off, I'd just like to state how wonderful the concept of this is. Centaurs run with the human torso upright, like a rider on horseback (which is the origin of centaurs, riders mistaken for mythical beings). I like that you've integrated the feline movements into the human torso; the fact he is also running with his hands is very unique.
I see that you've put in the artist comments that you may revisit the tail; I think that would be my only critique as to the over-all motion of the creature. Tails serve the same purpose as capes in superhero comics: To emphasize the motion of the figure. I think if you just put a tiny bit more wave into the tail, it would give the figure more motion.
My only other critique is on the anatomy of the figure. This is just my own opinion, seeing as artists are allowed to have their own interpretations of mythical beings. But from what I've seen the collarbone of the animal lower half replaces the human half's pelvis. Just by your drawing, it seems that the collar bone of the cat body is at the bottom of the human torso's rib cage, which possibly limits the human torso's ability to be upright and makes for a stiff motion. His back bone is very short along the ribcage, so there isn't much motion that would otherwise be found in the lower back. My suggestion would be to add the lumbar spine by extending the human torso, perhaps another head width (from the nose to the ear).
Besides the anatomy thing and the tail, this is an over all unique and well executed design. It inspires me to work on fantasy creatures.
Nice work but your tail seems really stiff as it does not follow a path of action. Also something to watch out for, the legs and back "pop" into place rather than flow because you're missing a few frames.
Human wrists aren't meant to bare weight/ walk like feet however, if the hands were positioned like a wild ape (think Tarzan) perhaps the smoothness would improve? It looks awesome anyway, I could never do what you've done here