Google App Engine = World’s Biggest PDA
Here’s my recommendation for evaluating the Google App Engine: Think of it as the world’s biggest, baddest embedded device, like a smartphone designed by Chuck Norris.
Remember that, just like the folks that build PDA software, you are writing code to be deployed atop a purpose-built, specialized hardware/OS combination that has profound intentional differences from your Mac/XP/Linux desktop environment. And while the hardware/OS vendor (i.e. Google) does everything that they can to bridge that gap, many of these differences cannot be effectively abstracted away.
The teams that will successfully launch apps atop the Google App Engine are the ones that understand and embrace the nature of the platform (both pros and cons), rather than those that grudgingly work around its idiosyncrasies, pining for the Ubuntu-y goodness of their favorite deployment environments.
Folks who treat App Engine simply as an alternate deployment platform for Python-based web applications run the risk of hitting the wall before they get their app out the door. Anything but the simplest applications will likely require some serious RDBMS-to-”Datastore API” architectural transmogrification. And there are still a bunch of Python libraries (Paste, Mako, etc.) that cannot be used in the App Engine environment.
For time spent in the App Engine world will make for an interesting life:
Infinite scalability. Minimal administrative headaches. But no way to run a query with a “GROUP BY” clause.
Plan accordingly.