I wouldn't recommend a payment system that's still in beta. There's lots of things you can screw up that won't seriously damage your startup, payment isn't one of them.
I'd recommend starting out with one of the major "easy-to-get-started" providers like Paypal or 2co and then switch to a merchant account once the volume of sales make it worthwhile.
That is a good point that I failed to make in my excitement. Thanks for bringing that up.
Also stripe seems to be US only as well. As are most of these new payment gateway solutions.