The virtual academies in Ohio use it. It's supposed to be very good
. I pointed one single mom in that direction (virtual academy) due to financial restraints and she said they really liked it, although it was harder than the work her ds had been doing in ps (I think he was in 5th or 6th grade). I think they only did it for a year. I haven't seen it personally, though. I know I've heard a lot of families that go the v.a. route end up going back to ps because it's too rigorous...
I think it's a bit expensive if you just buy it outright.