Have you looked into PayPal? Yeah, they have their fair share of horror stories, but they have a decent API, pretty good docs, and they're quite reliable, too,

Have you looked into PayPal? Yeah, they have their fair share of horror stories, but they have a decent API, pretty good docs, and they're quite reliable, too, in terms of uptime. Their rates are competitive ($30/month, $0.25 / txn + 2.9% of the txn). I use them for my startups, never had problems.