Top Ten:
#1: Electronic Speed control (ESC). Remember the pre-Novak N-1 days...we don't wanna go back there.
#2: BEC (battery eliminator circuitry), you may not think about this, but once ESC's came to be, the Rx's had to follow and BEC eliminated the RX pack.
#3 DSM, no more X-tals...nuff said.
#4 Silicone shock oil. Works in all temps, no hair dryers to keep your shocks working.
#5 Personal Transponder. No more "brick" in the car, nice just to slap on track, check in and go.
#6 Pistol grip radio. I don't remember the days before the pistol grip, but I have seen the radio's you old guys used to use...they sure did suck.
#7 Brushless, no more brushes!!! Woohoo! Let's party!
#8 Li-Po, not main stream yet, but getting there!
#9 4wd, took many years and many different cars to get right, but all the most popular classes these days are 4wd.
#10 Peak chargers, just push button and wait, it stops on it's own...nice.