Yes,Retas Pro is used by many companies, 
american, european and japanese, like Toei!

You can even download demo versions of 
Paintman,Traceman and Renderman. (although you 
can only use the images provided with them) 

Pricey yes, but you get all these 3 programs 
together and they seem to be really good! (i 
think you can take some online classes in "how to 
use it" as well, not sure though.

anyway, just my two cents......
SEB