Has anyone tried the Rhino Ramps?

I used to have some of the old heavy drive up ramps and they worked pretty good. I saw some of the rhino ramps the other day and they looked quite appealing for oil changing to me. They supposedly support 12,000 pounds, and are made of structural foamplastic and I think they are only around 10 pounds a piece, which would be nice.

I may have to get a pair of these, anyone used them?