Sound on for me! I've customized all my ringtones and text tones so I like to hear them. I also have my own office at work, so it doesn't bother anyone. I only silence when I need to (theater, meetings, nighttime, etc).
This. It's the best way imo. Least distraction and when I want/am free I can check to see what's going on. I dislike people who have their phones on ring at work - very distracting and kills train of thought. Tho, it's their "right" so I won't yell at them.
Now, if I'm expecting a call or something important is going on - I'll have it on ring. But I buy my own ringtone because I find all the iPhone ringtones terrible.
FYI my iPhone spends 99% of its time in front of my keyboard so if anything happens I usually notice right away. Probably a big factor in why Vibrate is OFF and Sound is OFF.