RE: Spektrum DX-7
I don't care about the frequency control as that has never been a problem for me up here in Alaska. That said, I still like the idea of having a data link to the airplane where more than servo positions can be transmitted. Obviously the DX7 doesn't do any of this so I'm not even looking at that radio, but if the Extreme link stuff comes though and is proven to be reliable, I'll be all over it.
As far as peoples comments about the frequency band, it's all give and take, higher frequencies offer more bandwidth, and use less power, but are also much more line of site. Lower frequences are subject to metal linkage, carbon fiber, and other problems, but don't require as much line of site.
Either way, it comes down to reliability testing with your equipment on your plane. If it works for you then use it, but that doesn't mean it will work for everybody else.