[majek]

You don't have to use Java. That's exactly the reason I hacked together EvServer: http://code.google.com/p/evserver/wiki/Documentation

Because of GIL, there is no point of using multiple threads in Python. Scaling must be done through adding more processes. Than an IPC communication starts to be an issue - that's what messaging middleware is for. The sooner you integrate messaging with your project - the better.

Once you have a messaging platform - comet can be done in any technology you prefer, it really doesn't matter. That's because the scaling complexity is handled by the message broker.