Well it just so happens that KI is my favorite game, so getting it working is a big deal for me. I've got it working full speed with KIAME on my p3 @ 866 MHz. The sound gets out of line sometimes, but I've been working on ways to fix it.
In response to an earlier post, you do need the ki.img file, not the ki.chd (or whatever) file.
I also really like Cruisin' USA, but I doubt I'll be able to get that one going any time soon so I'm not holding my breath. I know they can be run at full speed, just not through MAME. Cruisin' uses about the same hardware as KI and I can get that running full speed.
MAME is going to run those games slow because it doesn't optimize for speed. It merely "documents". If I knew how to code I'd work on getting some of those other games going, but I'm not that knowledgable.