Ok, here's the deal, I'm one of the webmasters of a forum that has recentlly installed the smfshop. So far, there have been no flaws or anything like that but...
I created 4 new groups after the shop was installed. These groups had custom stars, another color in the on-line list and stuff like that and you could only join'em if you bought the item that allowed you to change membergroups.
However... the people from the new groups cannot acces the shop anymore
I searched to see if there was a problem with the permissions but i didn't saw anywhere a option that would disallow someone not to use the shop...
The funny thing is that when I tested the change memebergroup item with an "older" group, that had allready existed before the shop was installed it worked flawleslly. No problems. This problem has only appeared to the new created groups...