We were able to get our product off the ground right away with Stripe (we were in their beta before they opened up to all). It's extremely quick to implement, their APIs are well-documented, and I doubt they'd prove bothersome like PayPal is being here. In my experiences, their support actually responds quickly and goes above and beyond to help.
If someone from Xenonauts is reading this: let me know if you need any help implementing Stripe if you decide to go that route. You can tweet me at @michaelschade or drop me a note at hn [-at: @-] mschade [-dot: .-] me and I'll provide whatever advice I can. I'll also see about sending this suggestion through their site in case they're not HN readers.
Edit: found their email and sent through there too. Hopefully they can get the issue resolved–I feel bad for them not being able to accept orders right now, that must be a really upsetting position to be in.