Spreedly Core is a simple API-based product for processing payments and is PCI compliant via transparent redirects (like Braintree). If all you're doing is processing one-time charges, it might be a good option to consider.

Basically, your payment form posts to SpreedlyCore, which posts back to your server with a token. Your app can then perform the basic payment actions, including validation of the user's posted payment data (minus the sensitive info, of course).

The service supports several gateways, and you never see the customer's payment details. The API simplifies dealing with responses. The biggest pain is that it's XML-based.

Regardless, I got it up and working in about a day, and I am slow. :)

It's very easy to use, and though new, the team is very responsive, and the API follows most conventions of their Spreedly subscription service, which is more mature.

The only thing you need to bring is an SSL cert, but you were gonna do that anyway. :)