The Java and Python support for AppEngine is fantastic, but for two projects I want to do (my own projects, but may be revenue generating :-) I want a more agile programming language that Java and while my Python skills are sort-of OK, my knowledge of Django is very light.
I should probably just bite the bullet and spin up on Django, but I would strongly prefer working in Ruby. I have been experimenting with the JRuby + Sinatra + ERB + datamapper combination and at least an inactive web application spins up well within the 30 second request timeout window. I very much like datamapper (object identity issues) and it should not be too difficult to be completely portable on two platforms (given data import/export utilities):
- JRuby + AppEngine
- Ruby (1.8.x or 1.9.x) on any server
For future projects if I need lots of back end processing (map reduce, spidering sites, etc.) then I will stick with Amazon EC2. If I can get by with just a web interface and a data store, then I would prefer AppEngine (to save a little money). Two great platforms!