I think with Paypal you can put a button on your site to receive funds, where you will have to check and manually send out a link, but you need to work with a separate system (i.e. Shareit.com) if you want to have the system automate a temporary download link for the customer. I could be wrong and Paypal could have a nice system for doling out software and/or keys...
If it really is a unique and interesting game, you can try to contact Valve to put the game on Steam, as there are tons of indie games on there now, including one made with Blitz. From there you would obviously not have to worry about bandwidth and hosting, DRM, etc. but for a small percentage of your profits. This is the route I would go personally.
I've only released one game as shareware, WordZap, and I used Shareit.com. It's a fairly reasonable service but I have forgot exactly what % they take for royalties.
Do you have a trial game we can download??

Senior Web Developer - Nokia