Don't think I've got anything quite to the level of 50+ files, but I've done some smaller scale javascript only applications where the only thing done backend was a restful database wrapper.

I agree that it can help a bit, but I've tried it, and I didn't notice enough of a productivity increase to bother adding a compiler step.

I'm the type who would use and occasionally has used assembly (this was embedded stuff mind you), so I might not be representative.