I've been using X0 gripshifts on 2 bikes for a few years now and they've been faultless. I used X7 and X9 triggers before and thought they were poor in comparison (sloppy shifting and they failed on more than a few occasions).
Once you get used to them, gear shifting with gripshifts are very fast, and you can jump several gears in one twist, which is handy if you're going from a steep descent to steep climb for example.
I've never had trouble with accidentally shifting gear whilst holding onto the bars – something that I'm always asked whether I do get by others when they see that I'm using gripshifts.