Not much time to write at the moment, so I'll keep this short.
The new Expat bindings definately offer some nice functionality, and there will be more to come once I've found time to fix some bugs in Expat itself. There's no way I'll be able to get to that until after the Python conference in Long Beach. Anyway, the latest bindings are present in the Python 2.1 CVS tree and in PyXML 0.6.4 and newer, but you need to have the new Expat library pre-installed for the newer features to be used.
The weak references implementation for Python has just about been refined to the point where we're happy with it -- I need to implement support for rich comparisons for the proxy objects, but that's all that needs to be done that I'm aware of. The code needs to be exercised more to make sure bugs are shaken out. Martin von Loewis and Neil Schemenauer have both made very valuable contributions to the implementation.
Acquisition is still bugging me, but I can wait for another time to talk about that. I really need to work on my talk for IPC9.