There are others out there that do this. The most direct competitor is http://gumroad.com But any site that allows selling files such as digital river is really a competitor.
Gumroad looks a bit more polished but what I'm missing with all those services is some sort of browse section. (is that only after logging in?) ... Ok you can share it via twitter or other networks but browsing around makes me impulsively buy more than just seeing one link on twitter :)