Google App Engine has announced going out of preview (when were they considered a preview anyway?).
In doing so, they have introduced a new pricing – in other words, increased pricing.
Some developers felt they are forced to leave the service, because for them, the cost would have increased threefold, or 30 folds which killed service like PlusFeed. If you are one of the "victim", you might want to share your experience in this discussion.
Personally, I use App Engine for various small web apps and websites. Fortunately, I am not affected, because my apps have small usage.. If this change affected me, say if I need to pay $9/mth, I will feel cheated by Google. This is because App Engine has been widely regarded as a cloud platform offered by Google, for free.