Sehreen, Brown Alumna
Pros: The no-credit system allows you to take courses that you would otherwise be a bit apprehensive to take b/c of lack of experience/prior knowledge. It's also a good way to add a fifth course to a normal four-course workload while taking off some of the pressure.
The only con I see is misperception. For some reason, some people think that Brown students don't get grades at all.