Internet Explorer 6 and 7 render input buttons with too much padding on the left and right or render the input button's border too wide if the button's text is very long.
Restyle the input buttons using CSS as follows:
form input {overflow:visible;font-size:1.1em;padding:2px}
This fixes the button width problem in IE nicely and does not affect other browsers.
The important part is the first rule. It seems to force IE to expand the button to accomodate for the correct width. You can apply any font size and padding that you need.
Tip: Since this fix is for Internet Explorer only, put it into a separate style sheet to keep your valid code clean.