Looking pretty noice!
You may not have seen it, but the guy that started MakeHuman started up a new project that basically does a similar deal, but it's directly integrated into blender as an addon:
I think I prefer the meshwork it puts out compared to MakeHumans. May be useful to keep an eye on it
Performance is definitely a tricky thing to deal with for complex scenes in the current builds. We've got quite a few things cooking that should let you crunch a lot of static geometry really fast that you can probably capitalize on in the near future, but if there's any current spots giving you trouble, feel free to ask, may be some tricks you can use to optimize some trouble spots.