I have the saris bones 3, and its pretty good.
Few concerns with it though...
The tie downs need to be very snug or the rack will tip in a turn, or slide down the car. As such, the pressure exerted by the rubber feet has been known to scratch paint or dent the car. Beware of this. Also, there really is no way to lock the bikes.
I went for the roof mounted solution instead, primarily for security reasons. Thule sells various products that will attach to the standard roof rack sold by Saab dealerships. They offer key-locks, and they are very stable on the roof. Also allows you to use the trunk while the bikes are mounted (Saris Bones doesnt allow trunk use when attached).
With a roof rack, make sure you get a wind fairing though...helps to disseminate the noise and will prob help MPG a bit.