Here's a short list. I may add more later.
Pro: Yes, it is true that BW wraps up the story nicely. Still some plot holes, though. What happened to the Shield of Azunai? That's kind of important, seeing as you spent all DS2 getting it reforged.
Pro: Got a little bit harder. Elite still just isn't as elite as I'd like it to be, but at least it's not some joke. Strategy becomes more important, and the map is more appropriately rebalanced. Monsters now can use powers and special abilities.
Pro: Neat new weapons and armor, and the new classes make gameplay more interesting, especially for solo players. And who doesn't love dwarves?
Pro: New crafting system becomes more like what it should be, and recipes are a fine addition.
Pro: More autocast slots! Yay!
Con: Still too easy on Elite and Veteran.
Con: No chants on the BW map, meaning if you start with a premade party you run into difficulties. ??? also still pops up, and I'm unsure if you can use the stone he drops like in DS2.
Con: No skill point rewards. Also, no interesting rewards from the arena quest like the Light Naiad.
Con: Inn, enchanter, and several other useful things can't be found in any town but the Dryad Outpost. That's realistic, but kind of irritating.
Con: Nerfed items, skills, et cetera. Superpowered Elemental Rage no longer works, though I suppose that's for the best. Absorption also takes a hit.
Con: What happened to that Shield!?