I'm using the most recent version of WP and e-Commerce. (as of 2/8/13)
Paypal is set up as the payment gateway, but will not show up on the check out page. When you hit the purchase button it simply returns you to the check out page.
There are a lot of people posting the same issue on the plugin support forum, but no one ever answers there.
I have a client who is ready to open her shop except for this issue and I'm at a loss.