I've had a set for a couple of years now, and really like them. Very stable and they don't slip when driving onto them.
I bought one set of ramps with the matching 10" 'crib' blocks. I find the blocks hard to use since it's difficult to jack up the wheels high enough to get under the wheels...
I recently downsized from a 3-car garage to a 2-car garage. To make up the parking room, bought a Directlift Propark 8s - had it installed about a week ago.