shopping carts & such

[False Start Distro]

So, I haven't run a distro in years. And when I did it was before using paypal shopping carts became the norm, so I never really fussed with any of that biz.

I was reading through some of the threads on here and noticed someone mentioning that paypal carts don't allow coupon codes, but zencart does. Coupon codes would be nice, but I don't really know the difference between these two options.

So, my question for all ya'll is, what shopping cart system do you use and why? What are the plusses and minuses? Is it complicated to set-up and customize? Does it cost you money in any way?

Thanks in advance!