One customer wrote to me and said
It was quite easy. I only had to fill out about 1/4 of a page of info, I'm not sure if I made an account but it was so easy that other customers shouldn't mind.
So it doesn't seem like much of an ordeal.
One issue I am pinning down is a customer from Canada claims she keeps getting the error
[my account name] does not ship to this address
I sent her a DIRECT Googlecheckout invoice to see if she can pay that way. If yes, then the issue is with cartmanager not Google. I have received payments from Canadians and Europeans on a different Google account before unless this policy has changed. | 
