As a purchaser, I noticed over the past couple of years that I was frequently being redirected to DigiBuy (sometime hidden to a greater or lesser extent at the option of the Web site owner), and my experiences were always reasonable.
As a vendor, I started using them a couple of months ago, and (so far) have been pretty happy. Their take is a bit high (around 14%, including the credit card processing fee), but there are no monthly minimums or per product carrying costs. You can customize your site to use all or part of their services. The charge for your customer's downloading is quite
reasonable (pennies for megabytes). We've had no complaints from customers related to DigiBuy service in several hundred orders. Their server seems sometimes rather slow, but not unreliable.
Our store is at http://www.nr.com/com/storefront.html
Nothing fancy, but you can see how we've integrated DigiBuy.
Feel free to try it out by buying as much as you want