I have often thought about it. But I get really clean paint jobs just by wetting down the floor, and having a good fan blowing out the door... I just have to wait for a time when nobody is around so a bunch of cars getting hammered with over spray!
A guy who works in our industry has one. He said that it works pretty good, except it's slightly a pain to tear down. Takes two people to load it up. They are selling cheaper ones on ebay for like 3k the last time I checked. I slightly worry about the build up of overspray, then flaking off. But other than that, I'd say go for it and let us know how it goes!!