I think the problem was Google's Api was very ill written compared to Paypal's. This may be an old implementation, but I think the Api didn't allow subscription services easily, and also notified it's sellers of an order immediately (regardless if the transaction was successful or not).
Beside, I think Google is investing the proper resources in building Waller to be a formidable product against Paypal, Amazon, and other 3rd Party checkouts.
Side Note: For the Google Checkout devs that read this, I'm sorry for what I did (Michael Largent).
Shoddy API's are not unique to Checkout. Most, if not all, of Google's API's are actually pretty terrible. When they DO update their API's it's pretty rare that they tell anyone, and they never update their documentation. So, a workflow that worked fine last week will suddenly fail disgracefully and you'll have no idea unless you find the right version of the docs.
Beside, I think Google is investing the proper resources in building Waller to be a formidable product against Paypal, Amazon, and other 3rd Party checkouts.
Side Note: For the Google Checkout devs that read this, I'm sorry for what I did (Michael Largent).