I borrowed a Saris from a coworker; once I got over the notion of using the wheels to hold the bike in place (worried about tweaking a rim), I rather liked it. Only thing I ran into is that it does not work with fenders--my bike currently has those. Oh well. My coworker bought it as he has a suspension full carbon fiber mountain bike, and he didn't have many other options for racks. Worked well in a 1.25" receiver.
Speaking of receivers, I used one from Hidden Hitch on my Jetta. Works well enough. I think they have their installation guides on line. I didn't need much more than a drill and a couple of large drills to install mine.
Lastly, I'm not sure if the hitch mounted rack is better mpg wise or not. I think I saw like a 20% drop in mpgs. I did have my bikes installed as far back as possible, so that the hatch on my car would still open, so that obviously did not help. But I would have thought it would have been better.