> is the middle one still currently used?

That's the one I've been seeing for a while:

e.g. http://www.google.com/search?q=sd+card

The ads have higher click-through because the graphic attracts the eye. This is known to AdSense content providers, who sometimes put icons alongside text ads (a practice which Google disallows).

I can honestly say I have never seen a checkout badge. This is probably due to location, right?

[Edit: I changed the images in the post to use a screenshot sent by Tony.]

The old image of just a shopping cart is still being used next to sellers in Google Shopping searches.

10% increase in CTR, but what about an increase in sales? Any data on that?

Google is spinning this number – I've had experience with this specific type of icon before and the 10% gain is not true if comparing apples to apples CTR.

Google isn't actually saying that there is 10% gain in CTR. It's saying there is a 10% gain in CTR for "Google Checkout users", which in reality is probably some very small fraction of 1% of actual clicks.

It's also a metric that you could not possibly track and/or debunk, which makes the claim very easy to make.

Thanks Ben, I posted a new correction post!
http://blogoscoped.com/archive/2009-01-07-n80.html