I'm a new wordpress user (1 week now), and less than 24 hours into the cart66 pro plugin. I skipped the lite version. The cart66 plugin is exactly what I was looking for and the code is very well organized. I would have given it a 5/5 but I found that the UPS shipping module support only pulls published rates, not the negotiated rates you get when you have a formal shipping agreement with UPS. That required several hours of my time to figure out and upgrade the php code to work. As is evident with the 1 ratings before me, those users with no programming support would be out of luck. Cart66 Lite and Pro DO NOT support UPS negotiated rates. This means that you could lose customers if they are not happy with the higher shipping rates they'll be asked to pay. I'm very happy with the cart66 plugin otherwise and hope it is smooth sailing from here because I want to use it on another site tomorrow.