in one sense, not much - "detroit" as a catch-all for 'detroit metro area' (and in some cases "southeastern michigan") - that's generally fine. Economy is hurting, but suburbs are suburbs.

"Detroit" - the area within the technical city boundaries - it's decimated. It's not quite 100% gone - there are new pockets of activity springing up, but it's extremely depressing to see what's happened. Used to be home to close to 2 million people (IIRC), and now it's 700k, and most of those don't want to be there.

The "downtown" area - about 15 square blocks - is nice - then it becomes a wasteland for several miles until you hit the suburbs.