One headache i remember before the days of 2.4Ghz, was that the lower qualifying driver had to change his/her frequency in case it had clashed with the higher ranking driver IF they had run in the same heat. This was a major blow to the racing mindset and then you'd have to bring 2 pairs of crystals (minimum) to the race.

Not only during racing, its much more easier during practice and daily bashing to be using the 2.4Ghz system radios coz your car will never lose control because of a lost signal. no more frequency flags, no outta control cars...