The bedspread and raincoat names in my sig use shopperpress by premiumpress. I have about 10 affiliate stores that use it. It has paypal functionality, but it seems a bit quirky. For me, all of their themes seem to look better than they work, but the support has been fairly good so far, so I would still recommended them.
I get about a 1% conversion rate on sales, which isn't too great, but it could probably be boosted with better product selection and optimization.
I bought the full license, but I mainly use their shopperpress theme.
If you want a robust ecommerce platform, Magneto is probably the way to go. I plan on using it in the future for a non-affiliate ecommerce store.