When you loot an herb or mining node, your character now gains experience. It makes it very, very nice to level as a lowbie. Also, they changed tracking so that you can track multiple things at one-- so, you can take mining/herbing on one alt, and be able to track both types of nodes.
Also, they have changed what herbs/minerals spawn in what places, and it seems a LOT more streamlined/organized, and it's much easier to level or powerlevel.
Mages are looking GREAT right now for PvE and PvP.
Enchanting is a great profession for self bonuses, and engineering is a lot of fun, but some of the possible harmful effects of the toys have gotten a bit out of hand, and it makes them less desirable to use, because the risk does not equal the reward. If you aren't worried about mats, Jewelcrafing should still be a great moneymaker in Cata.