I demoed it today with my bassist, and he bought it (so he can write songs on guitar at home.) I was impressed, I think it's by far one of the best high gain amp sims, particularly for cross-platform, works well with its own cab or with IRs, etc. It's also very close to a Dual Rectifier sound, although it has a bit more of a solid state vibe to my ears.
It really completes the picture for Guitar Rig and puts it on more even footing with Pod Farm and Amplitube. It's also 10x better than Metal Amp Room and costs less.