I have always used the Agora Cart, OS-Commerce and ZenCart shopping cart software to provide my clients with their shopping carts.
After giving Digistore a shot, I have found it to be much easier to style than OS-Commerce and Agora. The default template structure is also more clean and usable than OS-Commerce's.
I would say it is very similar to ZenCart in improved Admin section and it's attention to improved user experience.
Negative: Hard to install for the inexperienced.