Easy Digital Downloads is great for selling digital products though WordPress. It's incredibly easy to set up and integrate with PayPal for free (other gateways are possible with purchased add-ons).
Pippin is an also excellent developer, he offers terrific support, and there is an active and growing community on GitHub contributing to the plugin development: https://github.com/pippinsplugins/Easy-Digital-Downloads
I use EDD on my site to sell themes and a couple WordPress development tools.
A killer feature for me in Easy Digital Downloads is actually one of the paid add-ons that Pippin sells. The "Software Licensing" add-on allows customers to get updates for themes and plugins directly through the WordPress interface.