Basically, it fixes compatibility problems with 3rd-party applications that modify the contents of the addressbook and datebook. Examples are Agendus, MyWeek, Supernames, etc.
Not everyone saw the compatibility problems, but it was infuriating to those that did. PalmOne sent a message about the update to those that reported the bug.
That's about it! The Brighthand forums are pretty good for questions about Palm hardware. They don't have anything like mobileread for reading software, though!
