There are a few things about Checkout to love. They take more responsibility for fraud than any other payments provider I know of. That has a lot of value, particularly for online retailers. The rates are better. They don't have the reputation for being shifty that PayPal has, though they'll probably earn one in time. When it comes to money, people get grouchy fast. Any mistakes, any perceived unfairness, any slight, will be trumpeted from the mountain tops (or sites like paypalsucks.com). It's just the nature of the business.

I've never had a problem with PayPal, and we have $10k+ in our account most of the time, and I've been using it since nearly the beginning of its existence.

I'm considering dropping merchant services payments altogether on our online shop and taking just PayPal, Google Checkout, and Amazon FPS. I haven't yet talked to enough customers to know whether this is a sane course of action, though.