I've been reasonably happy with Amazon Payments. One real benefit if you are on the receiving end is that people don't have the love/hate relationship with it the way they do with Paypal, and they trust Amazon to be safe, which can be a big deal.
I still prefer PayPal myself. One thing Amazon Payments doesn't have is an option for letting the payer choose how much to pay -- they aren't nearly as friendly to different kinds of payments.
We used to accept Amazon payment "donations" on DC but one day they decided they didn't like that, closed our account, and just basically gave up on attempts to resurrect our account. I was eventually able to create a new amazon payment account that we now use only for commercial license "purchases", which complies with amazon rules.