I have played around alot with the mental ray toon shader look.
In general the results are not very descent, and this aspect of mental ray didn't evolve much.
The renders are still a far cry from a fluid an elegant 2D cell shade look.
This animation was done 12 years ago in max by "Fortiche" (don't know how they achieve the lines with the fluid movement):
I consider it to have high production value but it seems that even after a decade, it's still not possible to achieve this in maya/mental ray. I hope I am wrong and that there are techniques and tool to achieve these results.