Best I can tell, all the others are taking the traditional approach to DC. They're getting it to work now due to advances in signal processing and digital tuning. Of course if it works, who cares how they get it to work. However these techniques don't yet lend themselves very well to software defined radio, and may have inferior performance to traditional super het radio and D2D's approach.
The other guys have an 11a card out which is impressive and shouldn't be taken lightly. However I've heard they're low in output power and don't run at the highest data rates. Any one looked at these personally?
Tampa, I've tested the 11a card and found it very impressive! Exceptionally high output power and very high data rates. Impressed the hell outta me. Revolutionary stuff Tampa. Looks like Parkers gonna miss the boat on this one.