[jbr]

It matters a whole lot what sort of payments you need to take. Is your payment model a sale (one-time transaction) or recurring billing?

If you're going to take credit cards and/or do recurring billing:

I've built two recurring billing payment systems (braintree and paypal express checkout) and maintained a third (paypal payflow pro gateway) and am most impressed with braintree's api thus far. http://braintreepaymentsolutions.com/ My braintree-based system hasn't gone live yet, so I can't say anything about long-term service, but their api was far more sane than the other two. That said, when we added express checkout to the payflow pro gateway, purchase rates increased substantially.

There are monthly minimums with braintree and a good bit of paperwork, but being able to directly take credit cards might add some degree of "seriousness" in the consumer's eyes.

If you're rolling on rails, you might want to check out http://railskits.com/saas/ (although I have no personal experience with them) and http://www.activemerchant.org/ (a payment library extracted from shopify).

If you're just doing one-time sales, you have a lot more options and the accounting is a heck of a lot easier.

[jwt]

Do you know what the monthly minimum for Braintree processing was? The last quote I got from them was $200/month if you're processing under $1mm/year. I've also heard of a couple recent cases in which it was negotiated down to $100 though.

[jbr]

I do think it's $200/mo, but as far as we've been able to tell, it's perfectly legitimate to run our own $200 transaction and pay the processor fee (a few bucks a month on $200). We've only had our merchant account for ~1 month, though, so I'll be able to tell you more at the end of the month