I am in the process of testing this plugin using WP 3.5.1, had no problem downloading and activating the plugin. Entered our Org Id as instructed and set up a form named TestForm. When I put the shortcode [salesforce form="TestForm"] update the page, then view it, the form does not show up in the page.
However, if I use the form widget in the sidebar, it works. Send info to our salesforce site.
Any ideas - compatibility issue with WP 3.5.1?
Thanks for the assistance.