There are many changes found in this incremental release from IBM. This one hour webcast runs through both the administration and development features for the client, server, Traveler and XWork announcements.
Webcast http://consultantinyourpocket.com/ciyp/ciyp.nsf/dx/replay-for-whats-new-in-8.5.3-notes-domino-traveler-ibm-xwork-server.htm and video replay