I know this is an old thread and a topic that will be debated forever, but I had to put in my two cents. I have a 95' rigid I use for street riding with 7-speed STX-RC rapid fire, which has never let me down and has not needed adjustment in 10 years, believe it or not. In '97 I bought a full suspension 8-speed Jamis Dakar which was spec'd with the first generation of gripshift ESP 9.0. I finally got it out of storage after 8 years and swapped out the shifters for the newer 9.0s with the SRS spring. After riding with them for a while, I have determined that RF is far more ergonomic. The grip of the gripshifters is thicker than a normal handlebar grip and becomes uncomfortable after a while. You have to move your whole hand to twist the gripshift--only thumb and forefinger for RF, while your other fingers can be operating the brakes. Clearly Shimano did think this out. I have tried the SRAM triggers on bikes at the LBS and the release lever requires an odd upward movement of the forefinger that just seemed uncomfortable and unnatural. I don't know what they were thinking.
What's more, I coordinate my front and rear shifting so as to reduce chain strain and keep the drivetrain running smoothly. To do this with gripshift, your rear shifter has to be twisted forward while the front has to be twisted in the reverse direction to maintain high with high and low with low. With RF and traditional derailleur, the gear indicators both move left for high and right for low. Much easier to visualize while riding. Again, SRAM didn't think of this.
And when it comes to changing shifters--although each manufacturer hopes you'll keep its shifters on--things break, or you might want to upgrade. With Shimano (at least with these older shifters), you can remove the shifter and leave the cable intact. Gripshift forces you to disconnect the cable from the derailleur and pull it all the way back through the shifter. Bad design--simple designs aren't always the best.
