I forgot to answer your question re: what is Ann Arbor like?
Ann Arbor is, I find, middle-class to upper middle-class and is not the most diverse town. Being a graduate student, and living on a grad stipend, is very doable here. UMich has many coffers of money for grad students (for conference travel and summer funding), so it is very likely that your initial stipend in your offer letter can be augmented.
Ann Arbor has great coffee shops (integral to the grad school experience, IMO). Mighty Good, Lab, and the Espresso Bar all serve quality espresso drinks. Others may differentiate in quality, but even to have 3 establishments so concerned with quality coffee in a city of Ann Arbor's size is a win.
Of course, the restaurants are great. A couple of microbreweries too. Ypsilanti (neighboring city) is where some grad students live as well for cheaper rent. They call Ypsi the Brooklyn of Ann Arbor's Manhattan... Make of that what you will.