I've tried several other WordPress e-commerce plugins, and previously had a developer's license for Shopp. I had a terrible time with all of them, and was ready to give up on e-commerce with WordPress altogether until I tried WooCommerce.
WooCommerce is incredibly flexible, well-written, and it just *works*. Just about everything I've needed to do, I've been able to do with WooCommerce. The extensive number of add-ons is excellent. I've used WooCommerce to build several fully custom sites and I can't imagine using any other e-commerce plugin.