ORIGINAL: flycatch
Battery technology has evolved to save weight and provide extended time duration. Nicad and Nimh don't measure up on these two accounts. New technology and old technology have there place in our hobby and should never be used as a sales gimmick. I have used both types but I prefere the old technology for safety and ease of operation.
I believe the newer technologies also improve safety through failsafes, higher data rates/wider channels, better signal quality and reduced susceptibility to environmental issues such as vibration.
Remember 2.4 GHZ is a shared frequency used by others in the communication industry. I still fly on 72mhz but only use the top end receivers and transmitters and have never experienced a problem.
You do realize that there are other 72MHz band users besides model aircraft, I hope. Wireless microphones, for instance. (Hopefully) unintentional simultaneous use of the same frequency by another pilot will shoot you down in an instant - with 2.4gHz, the equipment "time shares" and will ride through a collision with other transmitters. Even interference from adjacent channels and/or harmonics can disrupt 72MHz.
CW communications may be much easier to understand, but it's also much easier to shoot somebody down. The rules of the road for 2.4gHz ensure that far more users can access the band than was possible with old designs.
One thing that 2.4gHz equipment has done for you is that most of the modelers have moved up to it, allowing far fewer users to have to worry about at the frequency board.
Andy