- Mangle (Bear) will automatically hit up to 3 targets and is spammable (i.e. no cooldown)
- Cat form abilities cost 50% less energy
- Breaks Fear and makes you immune for the duration of Berserk
At first glance, Berserk is actually most intriguing as a tanking tool (although I'll admit I say that because I still flinch whenever I shapeshift into Tauren cat form. Druid form customization can't come fast enough). Popping this while going into a large 5-man trash pull, or while a raid boss is being Misdirected your way, is going to result in gobs and gobs of threat generation as you or a drinking bird spams your Mangle hotkey as fast as the global cooldown will allow. This also has the added benefit of rapidly advancing your early threat without having to resort to Maul. While Maul is, per rage point, still your highest-threat skill, it's a poor choice for early threat generation as it's very inefficient and you're virtually guaranteed not to have a full rage bar at the start of a pull.
Another benefit is that Mangle is one of three skills (Shred and Maul are the other two) that will apply and then stack the new Infected Wounds debuff. A full stack of Infected Wounds will reduce your target's attack speed by 10%, which puts it on par with the Warrior skill Thunder Clap (but not Improved Thunder Clap, which is currently part of the standard 8/5/48 raiding Protection Warrior build, so the two are unlikely to stack). Whether you take Infected Wounds will probably have a lot to do with how much you tank and the type of encounters you're expecting to do (e.g. on something like Four Horsemen you can't necessarily rely on having a Warrior around to keep Thunder Clap up), but the complementary nature of the two talents is something to keep in mind. It's a great talent for PvP but can find wonderful use in PvE as well.
On the cat end, Berserk is going to result in some fairly insane burst damage, as it essentially doubles the amount of Energy at your disposal for a 15-second period. If you're primarily cat DPS, you will want to take Berserk in conjunction with the Primal Precision talent much earlier in the feral tree, which will increase your expertise by 10 and refund most of the energy cost of a finishing move that doesn't land. You'll also want to time your trinket cooldowns to coincide with Berserk while Savage Roar is active; you will ideally want the -50% Energy mechanic active while at your peak attack power.
Blizzard is generally moving away from the model of tanks using low-damage skills with high-threat coefficients. This is a fancy way of saying that tanks will do a lot more damage in order to hold aggro, rather than doing less damage with skills that cause disproportionately high threat. We've seen that in the removal of Feral Instinct's current 15% threat boost to bear form damage (Feral Instinct in Wrath is now this), and you'll probably see the increased damage at work as soon as you log in after patch 3.02 goes live. One of the commenters on Elitist Jerks noted that a level 80 bear, with Berserk up, Glyph of Maul, and an AP trinket popped, is theoretically capable of hitting 4-5K DPS on any random trash pack.
And yes, the first picture accompanying this article is a Wrath bear Mangle crit at level 72 in tanking gear with minimal buffs.
Yup. We're going to be nerfed.