Tcher on WoW LJ comes through with an interesting change in the Wrath beta: mounts are now usable throughout Booty Bay. Personally, I've never had a problem navigating around there without a mount, but apparently it's a welcome change -- you'll be able to go all around one of the coolest cities in Azeroth without dismounting.
Even more interesting than the change itself, though, is the thinking behind it -- apparently Blizzard is still tweaking where mounts can and can't go. And though it's a small complaint, this has always been an area that's been a little confusing -- why were mounts fine to use in Ironforge but not in Booty Bay? Why weren't ships ever considered "outdoors," but the crates on them are?
At any rate, if Booty Bay stays changed through the updates on the live realms for 3.0, it'll be clear Blizzard is still tangling with their strange definition of "outdoors," and the rules on where mounts can and can't go, even in old Azeroth.