I met with a salesman last night, and it seems to make sense, but I'm no engineer. Basically, they drill a few holes in the center of each piece and use a hydraulic pump to pump a limestone slurry underneath to raise it back to where it should be. Supposedly the technology has been used for parking lots and highways since the 1920's but it has only become cost effective residentially since about 1985, with the use of carbon drill bits and good hydraulic pumps.

The advantage is that the cost is significantly less than new concrete. The disadvantage is that you have small caulked holes that don't quite match in color - I imagine they look like holes used for termite treatment.

I would appreciate any feedback you can offer.