I have Grip Shift on my mtb, and triggers on my commuter.

I really like the Grip Shifts. I find them to be more intuitive than triggers, easier to slam through multiple gear changes, and generally easier to deal with. No straining reaching thumbs. I do NOT find I mis-shift or shift accidentally when I have a death-grip on the bars in scary sections. (not that I ever mtb in "scary" sections anymore!)

The downside is when you ride 2 bikes with different shifters...I tend to get all be-fuddled, trying to learn how to shift again.

But, maybe that's just me.