Yes I've seen it. But it clearly shows some of the problems existing with GAE. It is possible to avoid them, as well as most of the rest, but we cannot deny the fact that there is a problem.
Also, there are read-only tests which are also not amazing.
But it clearly shows some of the problems existing with GAE
No it doesn't show that, because what we're discussing here is is not a 'problem'. The GAE datastore behaves this way by design. It may mean that some developers will experience problems, because they are not used to a non-relational database, but that only means they have problems. It doesn't mean that GAE has problems, unless you wrongly suppose, as you seem to do, that any developer should be able to use the GAE datastore as his relational-database-intuition tells him to.
Also, there are read-only tests which are also not amazing.