i always found that gripshift performed like the weather. ifs its fine, the gripshift is fine. but if the weathers shitty, then look out. i quite like the benefits, as has been said you can go right across the cassette quickly, and they were bloody light. but as soon as it gets muddy, then the cables get sticky, and as soon as your hands get wet or muddy, then you cant grip it well enough to shift the seizing cables...
nice bike tho.