Last year I set up a website for a non-profit organization. One of the requirements for the new website software was for everything to be able to be accomplished with just configuration -- no programming.
After evaluating a couple of CMSs I set up WordPress. I was able to download WP e-Commerce, install, configure and make a payment to myself with PayPal in less than an hour.
Our website just went through our busy time of year without any problems with the store or the PayPal interface.
Last week I was alerted to a problem with products in a certain category. The WP e-Commerce people got back to me quickly, sent my trouble ticket on to WP Support (I believe) and they fixed my configuration error. My store was back up running within 24 hours of my being notified that there was a problem.
WP e-Commerce is a good choice for anyone wanting a simple store on the WordPress site.