This is great news. The company I am currently working at is using the Google Protocol buffers within Python as well, and any and all speedups we can get is absolutely fantastic.
As of right now we are just getting off the ground and I don't think the protocol buffers are going to be our primary concern for a while, either way it is nice to know that in the future we can look forward to using these 3rd party libraries.
It is binary serialization format used and open sourced by Google. Unlike JSON, objects must adhere to a predefined scheme/structure, and hence, it is compact.
I mentioned that we were working on it too, so over the weekend I tried to make it usable by others.
Two main differences are:
1) Lazy decoding support: Message parts are decoded on the fly as they are accessed for first time.
2) No dependencies. C code is generated which compiles to Python module.