I'm trying to get the Google Checkout plug-in working and I have had some success, but have a couple of issues as well. I am using HikaShop 2.0.0 downloaded and installed on 28 November.
I am getting transactions to go through using the sandbox, however the status of the order is "Created" rather than "Confirmed". When this happens, the serial number is not attached. If I then go to the order and change the status to "Confirmed", the serial number is attached to the order.
In the Google Checkout plugin, I have set the field "Verified Status" to be "Confirmed", which seems like that should be the status.
We use the serial number to build a link that we promise will be accessible immediately after payment, so it's not an option to manually set the status to "Confirmed".