I had to get one for the last road trip I went on. Went with the Sportrack (Thule) 2" unit and a 1.25"-->2" hitch adapter. The thing is pretty solid, although for my comfort, I'm going to swap out the single rattle-proof bolt for a through-bolt (if anyone has one of these racks, they know exactly what I'm talking about).
Even with the extra inches from the adapter and the long post on the rack, it still won't fold up...and I only have a 31" on the stock spare tire mount.
This isn't a huge deal for me, as I usually have a Saris bike rack on the rear and will only use the cargo rack for trips. However, I'm also interesting in hearing if anyone has found a combo that actually folds.