I'm not going to limit anyone's creativity. Use the tools you have at hand, be it a good ray tracing program, 3D moeling program with rendering, DbPro, Bryce, or if needed a few touch ups in an art program.
Personally I don't see how someone using photo shop, or paint shop or any other image editor for a little post production is going to hurt, the same could be said for those who have a dynamic lighting HDRI capable rendering engine. (Is that fair to the photo-shop guy?)
I use bryce all the time, it's my preferred 3D rendering package, and I also don't feel bad if I do any post production in my favorite paint program.
How about this,.. if anyone does do any 'Post-Production touch ups' they should show a before and after rendering so we can see what was done 'outside' the 3D world. Does this sound fair?
Cheers!