I think it's a pretty cool concept. The idea is that an incorrectly set switch or dial could seriously damage very expensive headphones. The card has to be selected and inserted very intentionally before you power the amp on and can't be changed by accident when your uber expensive estats are plugged in and playing music.
I think I would forget to switch cards all the time. It only makes sense to me for people who only use electrostatic headphones with the same bias (all of their headphones use STAX Pro Bias, for example).
For me, this thing is too ugly to even consider. If it looked better and had a built-in DAC, making it truly all-in-one, I'd be more interested.