Enhanced AI! Well, sorta. All creatures seem to have improved pathfinding, but move extremely slow as a result of it. All magic casting creatures have enhanced spell casting. Basically, if they have the mana to cast it, they will, regardless of what their magery is. Nightmares and dragons alike are casting flamestrike and energy bolt. Even prepublish pets get enhanced AI. However, monsters seem baffled by the invisibility spell. I'm not sure if this is good or not.
Extensive tests have shown that pet AI and pathfinding is very poor. There are times when it shines, such as when a monster is trapped on a ledge and there is access via ramp. I have tested pets that were guarding as well as those told to attack. In both cases, pets will not walk all the way up to your desired target. Guarding pets will move maybe 2 tiles, then stop unless they hit the target with a projectile weapon (breath or magery). Pets told to attack responded similarly. When pets were told to follow targets they were attacking, they would walk towards the target and stop a few tiles away. Pets that attack on their own free will seemed to have the best response with going after a target.
Moonstones between the lands are scarce. Felucca lands (PvP+) have an abundance of stones (probably due to the fact that they were allowed to circulate for a while), while Trammel (PvP-) citizens have a difficult time of finding return stones. How can you remember the name of the lands you're in? Felucca = Fall (since all trees in Felucca are barren, unless you have desolation turned off).
A second lands gives the opportunity to have 5 more mare spawn points. Trammel mares will not block the spawn of mares in Felucca, and vice versa. On most shards, I do believe that the spawn in Trammel is already locked and secure. I wasn't able to be online at server up the morning Napa was published, but Hope couldn't find any in his travels to the new lands.
From what I can tell on Napa, all stablehands have changed names as well as appearances. Don't be alarmed, though, they still carry all pets. I was able to claim all of my beloved pets the day of the publish, and have been claiming Shona every so often to be sure (and to hunt up some of that enhanced loot!). Stablehands have a tendency to wander now and on some shards, have taken to seeing the sites of the town. If you were on one of the shards that got published earlier in the week and have lost pets, I feel for your loss.
Pets loose loyalty significantly faster than normal now, depending on whether or not they can see you. Once a pet looses line of sight of you, they will begin to "look around desperately." When this happens, loyalty drops like a rock. Beware of freshly tamed creatures loosing sight of you. I tamed a fresh nightmare and when i went around the ledge it was on to find a way up to feed it, it lost sight of me and went wild.
The all commands when used with a [target] cursor has been fixed. It no longer stores commands to be called up later. When you use an all command with [target] cursor, it will give you a system message that you can't use the all command with a target cursor and the last pet that was commanded will follow your command.
Any creature that has the ability to poison naturally (spiders, scorpions, snakes, wyverns, etc.) is now immune to it. You will no longer be able to spar scorpions with eachother for veterinary gains (which were hosed anyway, due to the last publish). These changes are now reflected in the veterinary faq.