Not usable for my needs due to a maximum of 10,000 insertions per day and 10 executions per second.
but with that said, i still play with it since i have faith it'll mature into a full platform. and if nothing else, it's a free hosting service for experimental websites, bringing down the barrier to entry officially to zero.
But note that these quotas are bound to change, they ask for feedback on precisely these issues, task throughput per day and task length, on the Overview page: http://code.google.com/appengine/docs/python/taskqueue/overv...