I've been doing that lately when I don't have time to go into the darkroom (I don't have a fixed darkroom space, so setup time is a bit of a barrier). The results look different on screen and are only an approximation, but it's a way of "rehearsing" before going into the darkroom. The image I have up right now in the critique gallery is one such image.

I don't actually try to determine actual exposure times, but where I might dodge/burn, or approximate contrast grade to start with, or what lend itself to split-grade printing or require burning at different grades.