Have had a Thule 9503 for a few years now.
Nice and easy to fit the rack to the ball, but can be a right sod getting multiple bikes to play nicely with each other on the rack, especially if they are of varying sizes.
One bike on is really easy, two not too bad if you use the inner and outer positions but 3 can end up with bars, pedals etc rubbing like hell on other bikes or a mish mash of rags and pipe lagging used to keep them apart.
If your wife, like mine keeps leaving the wheel straps undone them driving around they drop out so you need a collection of toe straps handy.
Basically, great for one bike or maybe two. Rack to car is peice of cake, slightly fiddler bike to rack, has lasted for years and still looks new apart from the none captive wheel straps.