I live in Iowa City now. It's a pretty safe town, as it's not too big. I would say, as always, just use caution, as there are the occasional assaults on campus, like any other college. Just last week we had an aggravated robbery in the middle of the day in a neighborhood near campus, but before that, we hadn't had any Hawk Alerts in a pretty long time. I've never had any problems in IC at night, but I wouldn't be walking around at 3 or 4 at night alone; it can be a little eery. Cabs are ridiculous here, but sometimes it just makes sense. I'm not a big fan of the area past Gilbert St towards S. Johnson, but that's just me. I've always lived before Gilbert St. Living downtown is convenient, but it can be a little rowdy. The area over on the West side (where a lot of grad students live), is pretty nice. During football season though, it can get pretty crowded, as there's people all over the place (naturally). Generally though, it's much quieter over there. Overall though, IC is really safe. There's not a lot of crime in general.
