I'm going to be implementing Comet in Python (even though I hear good things about erlycomet I'm not thrilled about supporting an Erlang-based web server in addition to everything else in our back end). I've found several possibilities:
(there are also some other choices that interface with Java servers, but I'm not interested in those)
Can somebody make a recommendation among these implementations, considering performance, community, and ease of implementation?
I am personally using Orbited, both because I am already using Twisted and because it seems mature. Twisted has a nice long history with many users, especially in comparison to Diesel and Tornado. Orbited is indeed built on Twisted.
There is a good blog entry covering an end-to-end orbit solution here. It sends data from a python script to a STOMP server (MorbidQ) to Orbited to Javascript - rendering that data as a graph.
Tornado seems pretty new to the scene, I couldn't find twisted-comet and I hadn't heard of diesel. I particularly like the way that Orbited can forward any sort of tcp/ip but makes it easy to hook javascript clients in with a message passing STOMP backend.