I'm just the opposite of you. 99% of the time, I've got it set to ringer (no vibrate) because I work in an office with a decent amount of noise (and the phone is usually laying on my desk). In fact, the only time I put it on vibrate is when I'm out to dinner or something like that, so as to not disturb people around me. I only put it on silent on Friday and Saturday nights, so I can sleep in the next morning and not be disturbed.
I will say this about the vibrate...I like the motor they use now in the 4S much more than the one in the 3GS. It's just got a better feel to it and seems to be stronger.