I did! Michigan puts together a FANTASTIC visit weekend--they treat recruits really nicely. The facilities are pretty awesome, the labs are nice and very well-equipped. One group had their own XPS, another a (really nice) diffractometer. The buildings (3, all connected) are confusing, but mostly because they're so large as a complex. The research impressed me a lot, and UM does seem dedicated to its chemistry department. Many of the current grad students were pretty cool, and everyone I spoke to absolutely LOVED Ann Arbor as a city. It's a nice place to live, and not too expensive. Lots of awesome microbreweries, too.
To be honest, the only thing that really put me off the place at all were some of the other prospective grad students--a few were very nice, but some came off as a bit self-absorbed and not all that friendly. Several profs did mention that UM has extensive support for first-gen students, but after enduring a long "where did YOU study abroad" discussion--largely with other prospectives...it was apparent to me that I'd do better in a more laid-back department. Still, I would probably be dead-set on going to Michigan if I hadn't just visited a program that was a *perfect* fit for my interests. Awesome chemistry there.