Maybe they do a great job once they show up, but I could never get that far. I was scheduled to have my car detailed three times and they never showed or bothered to call and tell me that they would be late or needed to reschedule. I've now wasted 6 hours waiting for them to show up to my house without so much as a phone call from them. At last check I was "the first on the list to be done," but haven't heard from them since, even after leaving several voice mails.
If you've got hours to waste and don't mind getting jerked around, go for it. Otherwise I'd recommend another mobile detailer.