I've been playing with it for 30 minutes (and I know that, because the demo just quit on me), and I'll take it upon myself to report that GR2 is almost identical to GR1 in terms of high gain stuff. I happen to like GR1, despite the fact that it takes an awful lot of work to get the "amp covered with angry bees" sound under control, but if you thought GR1 sucked at metal, then you'll think GR2 sucks at metal, too. The new presets are pretty BLAH as well in the metal department, but who uses presets anyway? (I'm also convinced nobody at NI has active pickups, or has ever switched to their neck pickup). The only "metal" preset among the new ones I even remotely like is the "Marilyn is Beautiful" one, oddly enough, and even then it's really just a semi-neat effect (super-fizzy industrial buzzsaw noise, but fun nonetheless).
The new synth and modifiers stuff is pretty damn cool, though. A run throught the MDF preset bank is a neat trip. All sorts of sequencers, envelope followers, LFO's, you name it. "Arpeggio Delays" + sustained notes = fun, and the "Trem/Dance Kik" preset is instant techno groove. Some fucked up stuff can be created by messing around with these sequencers.
So it looks like this is basically a super-FX update, and not really a leap in terms of guitar tone. The added functionality of "High Res" mode, though, is pretty awesome and something I've been wanting since 1.0; basically, GR sounds 100X better when it's run at higher sample rates, and now there's a button that automatically upsamples to 96k safely in the comfort of your whatever-sample-rate project. Pretty neat stuff, but not quite
enough for most.