While I suspect they won't make it a habit of raising the price from here on out, the more I thought about it the more I've come to the conclusion that it makes sense to go with providers that use more standardized software stacks (despite how great not having to sysadmin is and the easy deployment from Eclipse to GAE), because that way I can take advantage of future competition of providers. If I go with GAE the costs to switchover become greater and greater the longer I'm there... so while they may never jack the price UP on me, they'll have little incentive to bring the price down due to increased competition.
They seem to do a rare (once a year or so) push of whatever they've developed into a public source repo, and then just leave it there. No updates, no bug fixes, no community involvement, etc.
Their site looks like they're trying to sell me something, but there's no commercial product in evidence. And the whole thing seems to be done under the auspices of a university.
There's a link to their supposed development branch, bizarrely on launchpad instead of Google Code where they seem largely based, but it's empty.
I'm not really inclined to put time and effort into something whose model and motivation completely escapes and/or scares me.
I also now note that there's a "Contribute" link at the very bottom of your main site.
If I may make a couple other suggestions:
* Fixing the "Development Branch" link on your page (it's in the "Download" menu) which confusingly points to this totally inactive URL: https://code.launchpad.net/~cgb-cs/appscale/appscale
* Making some sort of statement on the Google Code page about your development practices and the fact that the bleeding edge is on Launchpad. People like me go to a Google Code page expecting to see the development site, complete with an active source tree, and get very confused when that's not what it really is.
also to fight vendor lock-in, Python developers can create Django apps then run them on App Engine using django-nonrel or on any traditional hosted stack supporting Django; or move between then w/minor (settings.py) changes; don't forget data migration as well.
If you're concerned, use Django-nonrel, it's been amazing so far. Otherwise, appscale sounds like a good alternative.