Seems to me that one cannot pass personal details thru to Google Checkout. As in when an end user types in their personal info and delivery details, they have to type that in all over again when they get transferred to Google Checkout.
 
Is this the case?

Hi Andrew,
 
Unfortunately Google Checkout API doesn't provide standard interface to pass through personal/delivery details.
 
As an alternative you can add several Delivery addresses in your Google Checkout account and then select one of them during checkout process.
 
WBR,
ViArt Support Team