Hi,
I have no experience with paid webcarts, but have used two free versions, both of which work great IMO.
1) ZenCart - comprehensive and a bit of a learning curve, but everything is 100% open source and there are countless open forum posts with free assistance covering every topic. It is really one of the best documented webcarts around and everything is free.
2) WooCommerce for wordpress. Very easy to get started, new and sleek design. However, you will need to pay for certain upgrades and forum membership. But the basic version works well too, I've been using it for a couple of months now and no problems what so ever. Checkout is a breeze.
Both carts are based on php; I would actually say the programming structure of ZenCart is easier than that of WooCommerce once you get into it. I had no programming experience whatsoever when I set up ZenCart.