Stat and Itemization Changes - Tanking & Physical DPS
I'll speak to what I
know here (Tanking & Physical DPS):
Defense going away - meh. Blizzard's intention here is that a Warrior or Pally can be spec'd DPS (Fury, Arms, Ret) and "Tank" a heroic in Cataclysm. Pop on a shield and be G2G. The same applies to a kitty druid shifting into bear form or a DK going into Frost Presence. However from what I read a few months ago, this will be adequate for tanking a heroic (present day lvl 82 boss). This will not be adequate for tanking a raid (present day lvl 83 boss). Supposedly to raid tank in Cataclysm you'll need to be spec'd deep into your relative Protection tree.
A few of my concerns with this path. Take a Fury or Arms warrior for example. Tanking a heroic they lose Shockwave, Vitality, Damage Shield, Heroic Throw/Gag Order, Intervene, etc. It will be TBD how this all works in practice, the PTRs, and Cataclysm Beta of course. My other concern (which is already evident with the new LFG system) is this will create many players calling themselves a tank with little or no tanking experience. Also, why go down this path when we have dual-spec?
ArP (Armor Penetration) and AP (Attack Power) going away: 
I personally find Stat Balancing an enjoyable part of the game. Take my hunter for example. It was relatively well known that until you were Ulduar 25 Geared (or better) Survival was the superior raiding spec. However, once you were able to get a static Armor Penetration rating of 360 or more, Marksmanship began to outperform SV. Fury Warriors enjoy similar ArP benefits and for me having to carefully analyze whether or not a new drop is an upgrade is just part of the game. I will miss this complexity and hope other opportunities exist in the future to make gearing/enchanting/gemming choices meaningful.
I am guessing there will be many changes on the horizon and Blizzard will be instituting many of them in advance of Cataclysm's release. I'm also confident their testing will be exhaustive. That being said, I will be watching with anticipation and a bit of skepticism.
