I've heard it ranks as the largest tourist attraction in Michigan, in terms of people/year or $/year.
Tyree has a pretty interesting footprint around the city. You'll be driving around the near east side, still blocks from the epicenter, and see buildings with large dots. My current favorite piece of his is the
yaweh house.
For a while he was doing these paintings on car hoods. There's a nice one at the recycling center -- it just says "our hood" in his bold style. Although I might be fond of that just because I really dig the atmosphere at the recycling center -- last time I went they were blasting classical music, really loudly, at noon on a wednesday in a fairly dimly lit warehouse.)