I have used a raptor rack for a year now. It is very easy to use, and securely holds the bicycle in place over highway speeds and rough roads.
One negative is that it clamps to the bike's downtube. It caused a scratch on my Fuji due to the derail cables being pushed into the tube.
I now use a rag or a piece of foam between the cables and the downtube.
When i haul my road bike, the strap that secures the wheel in the tray doesn't contact the rim (because the wheel sits too low in the tray).
I remedy this by folding a shop rag between the rim and the strap to take up the slack.