My life got so much better when I switched to Woocommerce. If you're not using Woocommerce right now, I just thought you should know because it could happen to you too. The transition to Woocommerce was faily painless, especially compared with what we routinely had to deal with using our previous shopping cart.
The code is well written and not buggy, unlike any of the other shopping carts we reviewed. As a result, it's been a breeze to work with and to extend. Enjoy!