This update contains various bug fixes that have been made over the last three years (the prior version on the Download Center was from April of 2007). It also has some changes that make it work better against Exchange 2007. For instance, the old versions of PFDAVAdmin expected certain directory objects to be present for all Exchange servers. In Exchange 2007, some of those objects are only present with a CAS role. This resulted in a situation where PFDAVAdmin would only connect to Exchange 2007 mailbox servers that also had the CAS role. That problem is fixed in this version of PFDAVAdmin, which has no problem connecting to Exchange 2007 with only the mailbox role installed.
The dependency on .NET Framework 1.1 remains, which means you should run PFDAVAdmin from a workstation with Framework 1.1 installed - you should not install this old version of the framework on your Exchange servers, because it makes IIS unhappy.
PFDAVAdmin still cannot connect to Exchange 2010 servers, because WebDAV is gone from 2010. If you need similar functionality for Exchange 2010, use ExFolders instead.