I think this is just part of Google's push to become more of an OTA. I read something about it a while back, and I think there was a suggestion that it wouldn't be counted as third party, but I can't find the article now.
I suppose there are some advantages in that it should be marginally quicker and if Google is handling payment, more secure, but I'd still probably book direct. Then again, sometimes Google brings up some great prices which disappear once you click through to the airline's website, so maybe there will be some opportunities there!