RE: WHICH RADIO TO BUY????
Depending on how serious you are with this stuff, the new Airtronics SD10G ($500 with 2 receivers) is really hard to beat, especially for guys who like to fly sail planes. It has more sailplane capability than virtually anything ever before. I have the pleasure of living a few miles from Northeast Sailplanes which many of you know about - Sal (the proprietor) is completely bonkers over this radio, and Sal likes nice stuff!
Some of the capability it has involves Crow - if you set up the plane with crow, the radio still has the ability to proportionally control all the surfaces for no loss in control. Apparently the other radios lose some control/capability when crow is deployed.
It also has the longest range of any radio on the market, which came specifically at the request of the sail plane community.
I fly in pattern contests and really like this radio a lot. I've been talking to the pattern community and everyone who has held one really likes it, a lot.
If you want to spend less money, the RDS8000 is a decent radio - a lot of bang for the buck. I had one but it was missing a few features that I really wanted for contest flying. I think you can get one for $150 right now, and it has some good heli features as well.
Spektrum DX-7 is possibly the most popular radio on the market - it's really nice; you pay a few extra bucks, but the quality is there. Our local heli-pro is flying one. He flies in contests too, so he's looking to upgrade, but it has held in there this far...
2.4ghz is just the frequency that the radio operates on. However the new radios that operate on 2.4ghz all have a rapid channel selection system in which they are constantly changing frequency (very rapidly) so that other radios can't interfere with the signal. There is no more worry of being 'shot down' or shooting someone else down - it is really nice. Other than that, the radios are pretty similar to the FM radios - there are nice computer radios and there are inexpensive, minimal radios.
Hope this helps!