[jakobegger]

I can also vouch for Fastspring. The reseller part is really important. It means they take care of billing and VAT, similar to the App Store. It's a bit more effort to set up compared to the Mac App Store, but they take less and pay out faster. Customer support is really good. Their API is a bit annoying to work with, but gets the job done, and the customer support makes up for unclear docs. I'm really happy with them.

[matheweis]

I'm not in the same boat as OP, but I definitely can vouch for Fastspring in general. It's extremely convenient from the business standpoint that I don't have to worry about all of the complex international tax laws, etc.

Also, I've used PayPal API, and found the Fastspring API comparatively easier to use once you figure it out.