We are about to start working on new commercial web project and considering Google App Engine as a potential platform. Questions: Does Google App Engine is really scalable and may be considered as a production platform for commercial project? Is it more expensive (or cheaper) than good hosting company service in long run? Is it possible (and pretty cheap) to move the app from Google App Engine to independent server/farm (e.g. to use it as a private system, to exploit our own hardware etc.)? Is there some mechanism to deal with DDoS attacks? Can I make a full backup of the app data? Sorry for such silly questions.

Google App Engine as production platform

We are about to start working on new commercial web project and considering Google App Engine as a potential platform.

Questions:

Does Google App Engine is really scalable and may be considered as a production platform for commercial project?
Is it more expensive (or cheaper) than good hosting company service in long run?
Is it possible (and pretty cheap) to move the app from Google App Engine to independent server/farm (e.g. to use it as a private system, to exploit our own hardware etc.)?
Is there some mechanism to deal with DDoS attacks?
Can I make a full backup of the app data?

Sorry for such silly questions.