What I found researching shopping carts is that PayPal is very limited.
If you are shipping the same type of an item and can use a flat rate - same shipping charge for all orders, or can use a percentage charge, you can use their shipping cart. It is somewhat labor intensive in the time required to develop your cart.

With something such as SunShop, you enter your information and your cart is automatically created, and infact, your entire site is created.
You only have to manually add pages for additional specific content.

I do use PayPal to accept payment, as you won't find a cheaper gateway.

Brian
www.Delcompusales.com