First it is all Python. It makes sense as I believe Guido v Rossum, Python creator, works for Google. Some people believe in a future Java application hosting. I don't see any reason why it could not become a reality. Making something like AppEngine is a big task, changing implementation language is not. In the meantime, it is not an excuse not to try it, as the Python standard library is fairly rich and Google provides additional libraries on top of it.
AppEngine offers the basic bricks for building web apps:
- Persistence: they rolled out their own persistence layer. Is it because it is stored in BigTable? It is quite basic (no join), maybe again for the same reason. Still it is enough to write prototypes or do fun stuff.
- View: one can use Django templates. They are not perfect but better done than what we have in the java world for templating.
- Authentication: Google provide their authentication system transparently. It is amazingly simple to setup authenticated sites/pages.
- URL Fetch: points toward service oriented architecture. Without it, making services and calling them would not be possible.
- Other useful stuff like Mail, cache.
With such a list of libraries, one can easily imagine the server side of future apps for Android running on AppEngine.
The way code updates are pushed to the google servers is a bit reminiscent of Java web application deployment. However it is done with much finer granularity (file).
Overall I am happy with AppEngine. Yes it is similar to old PHP hosting, but it adds a lot of value by bringing few easy to use libraries, and natural integration with Google infrastructure. Compared to a PHP hosting, I think the biggest improvement is the database (dev use and admin use). For the dev it is integrated to the code. For the admin, it can be done transparently on the web. The most interesting is that it's FREE.