Pylons is pretty neat because its really a framework for building a framework. You can pick and choose WSGI middleware and slot it all together with whatever templating engine or database abstraction layer you like. Pylons just gives you most of the glue you'd need - stuff like unit and functional test harnesses, request routing, caching, and various handy decorators. The Pylons approach has some disadvantages however, since its not quite as well integrated as say Django, which has more of a one-size-fits-all, monolithic approach. Pylons also has excellent documentation.
Its interesting that Turbo Gears 2.0 is built on top of Pylons. It seems to aim to provide you with a more consistent out-of-the-box solution - they standardise on one templating language (Genshi), one database abstraction layer (SQLAlchemy), etc.
It will be interesting to see where Turbo Gears goes from here. It could be quite compelling if the community catches on, but it seems to me that its a little late to the game. I'm not certain what jumping to Turbo Gears 2.0 from Pylons would buy me at this point, and I'd imagine many people feel the same way.
Niall O'Higgins is an author and software developer. He wrote the O'Reilly book MongoDB and Python. He also develops Strider Open Source Continuous Deployment and offers full-stack consulting services at FrozenRidge.co.Tweet