Stylus for almost everything, fingernail for the rest if I can't be bothered to take the stylus out. I never use my skin to touch the screen.

And I've had N900 for over 14 months and never once put the stylus in my mouth (I can't even imagine what's on it), nor have I ever lost it.

As others have said, being right-handed and using fingers is not easy. Most pop-up menus appear to the right of the touch, which means your finger blocks it. Using left hand's fingers also tends to cover the light sensor which makes the screen go dim. So using the stylus seems better for both kinds of people.