I have a love/hate relationship with building world geometry with 3d apps. It looks so much better but it can be a real pain in the ass to just create simple things that we used to do in five minutes in radiant. Once you mastered radiant's controls, you could really toss stuff together quickly. The world has moved on though.
I think if you can find correct scaling requirements for a specific app it wouldn't be so bad. You could just stay in Lightwave or whatever until you were ready to import everything.
The API look really nice for C4. I'm struggling through my CS degree (finally) so it's nice to know what I am looking at.