I just came across this thread (my ears were burning--someone should have PM'd me!).
Yes, I created my own website. I happen to be a web designer, so it was not hard... actually, it was a lot of fun.
I chose PayPal to handle my transactions, because of its sources of third-party scripts that make it possible to set up your own e-commerce system. I found a script that would allow a user to modify fairly easily, add the required scripts to their web server, and test it through PayPal. (The original script I used is no longer available... presently I use
Linklok.)
The PayPal part of it handles the money transaction securely, then sends an encrypted code to the script on my server, which generates an email to the purchaser (as well as one to you, notifying you of the purchase). The email has a randomly-generated download link that is valid for a limited time (which you specify). You must have the link in the email to access the files, so you can't go back and try to download anything else in there.
It works pretty well, being able to handle multiple transactions, and basically allowing purchasers to buy 24-7-365. It's not programmer-hard, but I would advise a good knowledge of HTML, your web server's file setup, and an ability to be able to set and reset permissions settings in your cgi-bin. If that's too much for you, you should hire someone to do it for you... if done wrong, you can open up yourself, and your web server, to security threats.
Feel free to ask any other questions, either here, or via PM.