I do not use google checkout now but thinking of adding it in the future. Does google checkout improve the adword ranking when showing the ads? Thanks,
No it won't. But if it improves CTR that would improve ad rank. (Not saying that will improve ctr - just that if it does.)
It tends to improve CTR in my experience, which in turn will improve quality score, which will in turn improve ranking. So no, not directly, but CTR increases may have the knock on effect of improving it.
Yeah it should improve CTR, because it makes the ad look more "official" when people see that Google Checkout icon. Plus it draws the eye to your ad. I say you can't go wrong using that icon. But always test to make sure.