The vis has been a big issue in the project. We've done many tries to get rid of the MAX_VISIBILTY_ERROR that was plaguing us. After fine tuning, we were able to get under the limit. There are hint brushes on iso-z which I think are helping us to do it (again many tries...)
As for the fps My laptop is a HP Tc4400, it's a great tablet PC

but it wasn't designed for gaming. So my intel GMA 950 isn't fit to win the fps contest.
As for compilation we're, for the moment, compiling in -fast (the last "...(test)..." in gtkradiant i think ). Which take on my laptop around 5 mins.