I have the saris bones 3 bike trunk rack. Got in bright yellow, was a PITA to get that, but its so unique that anyone who stole it would have to leave the area to liquidate it
I have been more than happy with it. It has not damaged my paint, but since I drive a 2008 toyota corolla, I am not too discriminating about it. The clear coat doesn't look messed up when I do have to take the rack off, but I don't really do much other than clean the area with a clean rag for when I have to remount it. As to the stability of this rack, if you tighten down all the straps nice and good, it is rock stable. I have driven 90 miles an hour in my car with my bike strapped up, and it didn't budge. Learned a new fact actually, the wind resistance of the bike mounted to the car will in fact prevent the car from going over 90 miles an hour, not that I'd get all that much more out of my car (or want to, it gets kinda dicey over 85
To mount it I simply use the two parallel ratcheting straps up top, and I have an extra strap made out of the same material as the ones that bind the rack to the car that I thread through the frame, front wheel, and the left vertical "foot" of the rack to prevent the wheel from spinning and to keep the bike from moving around any. I found that no amount of fidgeting with the seat-tube ratcheting bit would actually bind the bike down with no movement. The free strap I use keeps the bike in place and does not damage any part of the bike, just prevents any sort of lateral movement, rocking, or other undesirable movement while transporting.
You cannot access the trunk while it is mounted, which is a bummer, but I can manage. Another downside is security. I do have a long cable lock that I have to thread through a loop under my bumper and through the bike frame, front wheel, and rack itself, but thats a real pain, so I try not to take my bike into situations where I have to leave it unattended on the rack. If this is an issue for you, get the hitch mount version as it will be easier to secure your bike.
Ok long-winded, but to summarize, love my saris rack, and haven't regretted it at all. I didn't want to trouble getting a hitch installed since my car doesn't come with one, and as I park the car under a covered bay, I KNOW that I would come home tired and drive right in with the bike mounted onto a roof rack, so I went with the easiest option, the trunk mount.