I'm about to implement Recurly http://www.recurly.com/ on my own site, on top of PayPal Website Payments Pro.

Recurly abstracts my gateway's API stuff and stores payment details so I'm not tied to my gateway - much like I wouldn't use a Comcast email address to have the freedom to change TV providers.

Worth a try. Note: I'm a potential customer of theirs and have no other affiliation.