Driving brings its usual problems of idiots who don't know how to drive in the first place. But I would definitely have my own set of wheels. It makes it a lot easier to get around.
I've never had a problem downtown after dark. I guess it just depends on what's going on and the weather.
I have lived here my whole life and I still find it difficult to drive in downtown Detroit! Many of the streets are one-way streets, and as there is very little police presence in the city lately, I have begun seeing people continue driving through red lights, or stop for a second, look both ways, then roll through the red light. Another time I was driving at night and there were 2 man-hole covers that were completely removed, leaving huge gaping holes in the ground. Sadly, I watched a brand new Camarro drive right over one going about 40 and jerk/crash to a stop ashis front right tire sank into it. Sketchy :\ . If you are planning on driving, please, please, PLEASE be safe doing so! I have had too many problems driving in that city to even count them anymore.