at the beginning...
Comment by Massimo my tests show that a loop in Ruby is about 15 times slower than the same loop in Python. That was enough for me to drop Rails. I’d love you to benchmark Gluon (http://mdp.cti.depaul.edu) which should be even faster than Django because it allows you to byte-code the web app, including the templates, so there is no parsing or text manipulation in production mode. No other framework allows it.
