I'd never even heard of the MuseBox. I love the idea of it but from what I've just heard (on YouTube), well, let's just say that it didn't win me over, tone-wise. Still, that's the idea... a computer that isn't running the distraction and resource-hog that is Windows, and that's essentially what the 11R, Kemper and Fractal units are.
If PG did it right, though, I think it would cost an awful lot more than $250... and without expression pedals, at that. Would I like one? Absolutely! Would I be willing to pay big bucks for it? Not likely. No, I think I like my current setup... small, lightweight, great sound and capable of running all kinds of software besides the PG stuff, should I choose to go that route.