CernyM - 4:07 pm on May 4, 2010 (gmt 0)

We switched over and now offer only Google Checkout for domestic (US) customers.

Our shopping cart is older and we've heavily customized it making PCI compliance issues a huge headache.

Google's fees are competitive (though not offering monthly fee payment is a hassle) and we've not noticed conversion rate issues (yet, knock wood).