I use the ox both in my home studio as well as at live gigs.
In the studio I quickly get a sound that I'm after, without waking the neighbours. The mic-, cab- and room emulation in this device is incredible, just on spot. Unless you've got yourself a world class studio, with world class mics, acoustics etc. There's no better way than using the ox.
Live I also use it for FOH, this way I get a consistant sound and the sound that I want, rather than getting a 57 up on stage where you don't know how it's gonna sound.
All in all a perfect solution to these two applications.
Furthermore there's a great attentuer in this thing as well, so that's nice if you have a loud amp.