When I tried to activate eshop, I kept getting an error: "eShop requires that the wp-content directory is writable before the plugin can be activated." I had made sure all the relevant directories existed and that they were set to 777.
It occurred to me that this error might have something to do with the fact that my client's blog does not use the standard wp-content/uploads directory for uploaded images.
Under Settings/Miscellaneous, I temporarily changed the media folder back to wp-content/uploads, and was able to reactivate the plugin. Then I changed the media back to what it was before. So far it seems to be working.
It would seem that the plugin should pick up whatever media folder is used for uploads, whether it's the default folder or not.