Hovering over Buy Now / Add to Cart buttons reveals inconsistency in icon theme CSS

What I'm using:

#TwentyTwelve WordPress theme
#MarketPress plugin

What I'm seeing:

When selecting the icon theme from store settings > presentation, I'm noticing a slight difference in the CSS when hovering over the buy now / add to cart button. When hovering over the button, it changes from a beautiful, subtle button to a rounded button with bold text.

This is just one of those things that bugs me, so I'm going to look into it in effort to remedy the problem.

Note:

When using twenty twelve, opting to select "none" in the store settings > presentation area fixes this, but you don't get the cool little icons or horizontal alignment for your buy now button and product meta information (price, category, quantity).