As a workaround, you can remove the blank spaces on each end of the button, which has the effect of decreasing the jagged edges. This is accomplished with the following css and a bit of jQuery:
input.button {
padding: 0 .25em;
width: 0; /* for IE only */
overflow: visible;
}
input.button[class] { /* IE ignores [class] */
width: auto;
}
$(function(){
$('input[type=button]').addClass('button');
});
The jQuery is for adding the button class. A more in depth write up can be found here.