Certainly anything that's not a core Google product you should think hard about using. I got burned when they shut down Checkout. They gave me six months notice

Certainly anything that's not a core Google product you should think hard about using. I got burned when they shut down Checkout. They gave me six months notice on that, which was just barely enough to replace shopping cart, order management, and payment processing. The first two I now have in house, so no one can turn them off. At least this one's fairly easy to fix, but I think there will be plenty of people unpleasantly surprised on 3 Aug.