I recently went through this working on a buddy's bike. His DB Apex came with early RapidFire and they were giving his tendonitis fits. I suggested GripShift and put on a set of MRX for him. A few miles and we changed the front shifter from indexed to friction (lots of little clicks instead of three big ones were easier for him to shift) and he rode that for a while. Eventually went for a largish SunTour XC thumbie on the front to give improved leverage for the left hand and that works best for him.