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.
2007 Seven ID8 - Bontrager InForm
2003 Klein Palomino - Terry Firefly (?)
2010 Seven Cafe Racer - Bontrager InForm
2008 Cervelo P2C - Adamo Prologue Saddle