Web Payment System Comparison

There are a lot of web based Payment systems. Recently I've been looking into them to see what is best for small to medium websites. I compared the following:
Google Checkout
Paypal
Amazon Flexible Payment Service(Beta)
Authorize.net

Here are some Writeups about them with the conclusion at the end of this post.

Google Cart
Google Cart is new to the payment processing industry but they offer a Paypal like experience with easy to integrate checkout buttons and low rates: 2% + $0.20 per transaction
Google Cart also has a pretty strong company behind it ;)


Paypal
Paypal has been the staple for authorization online ever since it became the prefered method of payment for Ebay. It has a strong developer community and an easy to integrate option with checkout buttons. The fee Schedule is available here but they start off at 2.9% + $0.30 per transaction. Requires monthly quota to improve rate. Good security and also has a strong company behind it.

Amazon Flexible Payment Service(Beta)
Amazon's flexible payment system is still in beta but has a lot of promise with the chance to lumping together micro payments to save on processing fees along with an easy to integrate backend. There transaction fee for CC for transactions above $10 is 2.9% + $0.30. If it is under $10 though then it is 5.0% + $0.05 for credit card. Which is better because the flat transaction fee is only $0.05 so it will probably workout better but at the same time still pretty high. Doesn't appear to be a monthly quota that can lock you in at a fixed rate.

Authorize.Net
Authorize.net makes it hard to find the fees for transactions and has a bad interface for integration. Customer Support is Great though and responds very fast.


Final Comment
I'm going to try out Google Checkout as it has the lowest rate for what I am looking for and has an easy integration. I'll be interested to see how Amazon develops their platform and as always Paypal is improving. So conclusion is right now use Google Checkout or Paypal, wait for Amazon to come out of beta, and proceed with Authorize.net with caution.