Several of them around. My son built his house using PWF a few years ago, and having wood in the basement (lower level) is much friendlier and warm than concrete. Finishing off the lower level has been a picnic, being able to insulate the thick walls and then drywall, as well as easy to heat.
The only thing that has appeared to be a negative was the hot water heater setting on the wood floor. Apparently with the house so tight, and the shower fan running, it caused the gas flame in the water heater to be 'pulled' downward enough to cause the floor to get too warm. Raising the hotwater heater and putting mortar board down solved the problem (a fault of the heater, not of the wood floor IMO). Some people put hotwater heaters in closets on wood floors, so overheating shouldn't happen.
PWF have been around for a good many years, as seems they originated in the 60's. The concrete lobby has been pretty active against them, and I think pretty effective as well.