I'll be doing a few things to the CACHEBOY_HEAD branch after the 1.6 release which will hopefully lead towards a mostly thread-safe core. I'm also busy documenting various things in the core libraries which I haven't yet gotten around to. I also really should sort out some changes to the apple HeaderDoc software to support generating slightly better looking documents from C source.
I've almost finished the first round of code reorganisation. The stuff that I would have liked to have done this round includes shuffling out the threaded async operations from the AUFS code and building a proper disk library, sort of like what Squid-2.2 "had" and what Squid-3.0 almost did; but instead use them to implement general disk IO versus specialised modules just for storage. I'd like to take advantage of threaded/non-blocking disk IO in a variety of situations, including logfile writing.