The diary begins by recalling the history of mounts in the game, back to the very earliest days when they were barely implemented in time for launch. The notion of mounted combat went from insurmountable to a strict on-rails system to a much more free-form system. It also dropped several ideas along the way, such as momentum, horse attacks, and purely generic combat skills.
War-steeds will take some getting used to, according to the devs: "Probably the very first thing you notice when you ride your War-steed for the first time is that it moves completely differently than your standard horse or goat. The War-steed is a large creature and its part of a much larger system, one that requires some skill, time, and practice to master."