Button padding

The goal is a button treatment suitable for toolbars etc. and that provides:

button interactions (click,focus,etc..)
flexible styling options - including icon/graphic buttons
inline or block display by css
0+ padding on all edges around button content

Button with span.icon

should have 0 left/right padding so the background image on the button content touches the edges (but doesn't in FF)

DIV with span.icon (for reference)