I have just enabled GoogleCheckout but noticed that during the checkout process, the GoogleCheckout logo appears on the Cart page, and if the user doesn't see it/click it there, Google Checkout is not listed as a Payment option on the Payment page (just PayPal standard and Credit Card appears).
I'm not sure, but I think that it may be due to the fact that Google Checkout doesn't let you send address information, so having a customer fill out all that address stuff would be pointless. You'll get the address from Google anyway...
I agree with you that it seems like it is in the wrong place. I have seen other people move it to the end of the whole cart process, but unless you are willing to crack into the code you have to deal with it where it is - there is no setting to move it that I'm aware of.
What I'd like to see is the whole cart process changed. The first thing that you should have a customer do is choose their payment type, that would allow the program to make a determination on whether or not it will ask the customer for any addresses. Asking for addresses first is fine for larger sites (www.walmart.com) that use an integrated payment processor and know that they're going to need some addresses, but for smaller sites who use Paypal or Google or Amazon for payment, there is no need to ask for an address.
Part of the appeal of using those services is that you don't have to fill out your info over and over again for each site you want to shop at. Just my opinion...
This is going on my laundry list... I may get around to fixing it one of these days, if someone else doesn't do it first.