After trying it for a week or two I think the concept is good but that it is not quite ready.
Biggest complaints:
1. The need for the program to stay open for people to access your store. This is a big hurdle, paying for and setting up a VPS is a PITA. Specialized hosting services will become available for cheap eventually I suppose, but that kind of defeats the purpose in a way too.
2. I don't like the window UI at all. It might look ok for a Mac user, but for me it took far too long to even figure out that the weird red, yellow and green dots were the buttons to manipulate the window, and even now that I have used them a lot I still think they are awful, way too small and placed strangely. On the client for Windows I would want and expect the standard Windows GUI.
It is also highly annoying that the window can not minimize to system tray rather than task bar.
3. It's very buggy. The most breaking bug is that I find that sometimes the server seem to shut down without warning even when the window is open, and I don't notice it until hours later when I try to refresh randomly. But there are also plenty of smaller bugs, like some messages refuse to go away when I click "clear conversation", and at first it was impossible to type the symbol @ on some keyboards (this is fixed now).