Now, as an advertiser, you can do more than putting text or image ads on the Google search result and/or its publisher network, you can also make direct sell. People click on your ad, put the order onto the "Google cart", and hit checkout! Be sure to "checkout" the flash video in Google's blog entry. Oh I love that little blue cart :)
Yeah. That's the "GBuy" that has been speculated around the web over the last few days. It also ties together with Google testing Cost-Per-Action ads in Google AdSense, where publisher gets paid only when an "action" has been accomplished, i.e. item purchased.
Clearly Google Checkout is not yet in the scale of PayPal, as it is pretty much B2C with Google as the middleman. Who knows, when Google Checkout scales later, and it might be as easy to send money around as PayPal (mental note to myself, need both "PayPal" and "Google Checkout" donation buttons here :).
Currently not many stores are available. It makes Google Checkout a bit pointless, if one of its advantage is to consolidate shopping experience (one login, one checkout, one place to store credit card and delivery detail, etc).
Update: Oops. Just release that it is currently only open to US residents. You can still sign up, but probably won't expect to be able to purchase anything.