I wanted to signal two (possible) bugs that happen also in the demo site:
1) While on the cart page, hover the mouse over the "cart" menu (under the search box). A white rectangle should appear. Tested on firefox 17.0.1 and Chrome.
2) On firefox 17.0.1, If a product has a variant, when selecting it, the "add to cart" button won't draw its lower border (about 1px).