Which is prcisely its purpose, for use in cities.
If Dallas had a rail system that I could use just to get to work and back, I'd use it. Unfortunately it is not scheduled for my area until 2007.
Not just any city, it's gotta be a tightly packed city. If it's a typical Western city that's spread out far and wide covering it with a mass transit grid that's actually usable is too expensive. I can get pretty much anywhere in Tucson faster by walking than by bus, and even by bus unless I've got major attractions (malls, downtown) on both ends there's probably going to be at least a mile's walk anyway. Adding rail to the system wouldn't improve it much if at all. Not sure how Dallas is laid out but being in Texas I'm betting it's a typical Western city that has too many "major" streets covering too much territory. Mass transit is great in someplace like New York of Chicago, in someplace like Phoenix or LA forget about it.
I hear you! If Dart ever makes it up to my area of Collin county I'd use it. It makes more sense than a 45 minute drive to go 18 miles.
Semper Fi