I've been running around hyjal as a tank, and so far nothing can really hurt me. For trash using pulverize usually makes killing things a bit slower, but with lacerate only stacking to three, it's more reasonable to keep it up. If you hit pulverize and then stack lacerate to three, the buff from pulverize will expire just before the lacerate stack falls off, so it might be worth it to use on bosses. We'll have to wait for the number crunches to run it. I just got to 81 and got thrash, so we'll see how that works. As a bear, I take almost no damage, and I'm wondering if anyone doing moonkin or cat find the damage negligible or something to be careful about.
A neat effect that they added is some kind of ability queuing. Currently on live you can't trigger an attack until the GCD is up. However on the beta, you can hit an ability with about 25% of the GCD left, and it will go off, even if you push other buttons in between pushing the first button and the GCD actually expiring. I'm playing with very little lag, and it doesn't happen at all on live, so I assume it's some kind of tweak to help people with worse lag still do solid dps.