I've had twist shifts on my main bike since I was about 14 and they're still there. It comes totally natural to me and as a result whenever I ride a bike with trigger shifters it feels weird and I do something dumb like upshift in the middle of a hill by accident. I've noticed that some bikes have much looser grip shifters than mine has (trek 820 with stock shifters) and when I've ridden these I sometimes shift by accident, but never on my bike. I like the fact that there's two less gizmos on my handlebars (more room for the pretty gals to sit).