Some of these things (like not drawing the whole city when you\'re facing a wall) may be addressed by the next release. Using the MB hydlaa map on my Mac in the crystalspace \"walktest\" application, I get \"decent\" framerates (10-40 fps) considering my graphics card (a geforce2MX on a 700mhz Mac). In the real game, this will be slowed down somewhat, but it\'s a lot better than with earlier versions of the CrystalSpace engine.
The artists/developers have expressed some reluctance when it comes to fogging things out, but I agree with you in that it could possibly improve performance to cut out distant geometry altogether as a last resort. There are other techniques that can still be explored, and the focus of the current series of releases is not so much on speed but on getting the \"game\" working. Crystal Space (and planeshift) will continue to improve.