I am not using web2py. But I had a look at the source code and it's horrible for so many reasons. For one the database definitions as well as the views and models and I don't know what, are evaluated against a global dictionary of values. It feels like PHP in that regard (it's bypassing Python semantics in name behaviour) and is very inefficient and I could imagine that it's hard to maintain.
I have no idea where all that fuzz about web2py is coming from lately, but I really can't see a reason why anyone would want to use it.
What's wrong with Django or Pylons? What does web2py do that you can't do with Django in a few lines of code with a better performance, code that's easier to read and on an established platform where tons of developers will jump in and fix problems in no time if they appear. (Well, there are exceptions I must admit, but in general the developers fix problems quickly)