There is a list of plugins which are tested and recommended to be used with ClassiPress (found on the
resources page), and any other plugins outside of this is really up to the individual to test out. I couldn't give you a definitive answer on that particular plugin because I haven't seen confirmation that anyone is successfully using it at this stage..at least not that they have posted here.
In terms of other payment methods though, there is Google Checkout integration which is going to be available in a future release of CP, and I know of at least one other non-paypal payment method which a ClassiPress customer has successfully integrated into their theme with the help of a developer. This just indicates that you can customize it to suit and it really just comes down to your level of coding knowledge.
