RE: receiver choices
As far as I know, even the cheap off-brands, Corona, Assan, HobbyKing, etc. only work with like branded equipment. I've yet to see anyone offer equipment compatible with other brands. JR, Spektrum and some ParkZone are of course compatible (DSM2), but they are all Horizon products.
I believe there is a lot of firmware in the 2.4GHz radio equipment for the frequency hopping and code spreading algorithms, and for an off-brand to be compatible, they'd have to copy it, which would probably be copyright infringement. There are probably some patents protecting various brand name systems as well. That may not stop Hong Kong or China from making some knockoffs in the future, though!
I was hoping after Spektrum and Futaba came our with 2.4GHz systems, Airtronics and/or Hitec would license technology from one of them for compatibilty, but everyone is doing their own thing.