Yup, I can see the advantages to having a more stable system than a trunk mounted bike rack (for which you don't need a hitch). My car has a few scratches from the bikes because of the way the rack fits onto the trunk. But I consider my car to be strictly utilitarian.

The roof mount racks are pricey though. You can get a trunk mount rack for 3 bikes for the price of one roof mounted rack (plus you have to get all of the other paraphernalia, some of which you could get used from craigslist).

The trunk mount setup works very well on a hatchback and the bikes don't come into contact at all with the car body of my friend's wagon.

p.s. We've used the trunk rack on trips of over 300 mi. RT with no mishaps.