Not only that but listing things like "ability to easily read and write files from PHP" and "support for [..] mbstring and mcrypt" as new features makes me less inclined to try App engine for any PHP work as it seems even the most basic things like writing files and mcrypt require App Engine-specific code.
I'd much rather just deploy to Amazon's EC2/Rackspace/generic VPSs than have to add App engine specific changes to my code.