I don't understand, Helvetica Neue renders awfully at body-text sizes on computer displays. Unless you need the light weights, use Arial. It's Helvetica made to look good on computers under 16px.
"Proper". I agree with Oliver Reichenstein's argument[1], but Google does 13px and it's fine. The font-size in most desktop apps is less than 16px. Human's are adaptable. 16px is just more comfortable.