The editor used to crash a ton, but at this point it is fairly stable as long as I am not clicking away when an autosave kicks on. Saving often in multiple revisions helps as well.
Thanks for the notes. I'm gradually tweaking the lighting, mesh detail, and BSP textures as I have time to finish out the map. I know the texture set and modular layout is a large part of why areas look very similar. I wanted to grind out the gameplay and cover first before going in and doing the final visual wash. I might try to destroy part of the cathedral in a later version of the map, but getting the crash-prone terrain to work and finding creative ways to use the meshes to get the look I want are the big hurdles. Is there something special you have to do to prevent terrain from permanently corrupting the level? I've tried to use terrain twice now and both times it somehow corrupted my map so I get a crash every time I load. Luckily, I had a recent revision I could go back to.
Btw, Hourences' tutorials are a great resource along with icecreamyou.com. Those two sites alone helped me jumpstart my work in UE3. Having some UE2k4 xp helped a bit too.