Well I'm a Carrara newbie but having experimented (a tiny bit) with NPR, I'm looking forward to figuring out how to get some cool effects out of it. It appears to have more potential than Poser's Sketch Room, which unfortunately doesn't hide hidden surfaces or deal with transparency well. ToonPro! is a gem. To state the obvious, I've found that it works especially well with less-organic sorts of meshes and textures. It's fantastic for robot models for example.