It's so hard to answer the "what's changed" question, because they've worked really hard on the game. Over all it's a well-ballanced, exciting FUN game.
As for your questions:
There's still lots to do in the game. Tradeskilling and harvesting are the big no-combat activities, but I've noticved there's more than a few quests that don't involve slaying monsters.
Yes, there's mounts that are not horses! Wargs, flying carpets, and tinkered hovering platforms come to mind. There's also a really big variety of horses now. Some are quested, some are crafted, some are purchased with cash or faction.
Here's a warg. I don't PvP, no clue.
There's not really a "new" class system, they just took out the class/subclass bit. You start as a brigand or templar or whatever instead of as a fighter or priest.
Edited, Jun 29th 2007 4:57pm by Calthine