I’m a very happy Fractal Audio AxeFx-II user. Using it at live gigs (with two active full-range speakers or line-in FOH) as well as in the studio, where it also doubles up as the audio interface for computers. Works great not only for guitars but also with dual output instruments like electric harp guitar or CHapman Stick, where you typically run two parallel virtual rigs. I even make flute patches (for mic input) in my AxeFx. As for IRs, I’m happy with the factory packs.
To me the most useful aspect of the Fractal is its extensive modulation options. That’s especially great when I play electric cello through it, using the instrument’s amplitude (how hard I’m bowing) to modulate the pre-amp overdrive. Can get extremely expressive 🙂