Well having read about them it does have dual signal paths or at least 2 amps you can choose to use, it also has flexible fx chains like the M13 and all the fx of the M13 assuming you get the HD500, there are 10 lost each time you go down a model.
Personally I got the email about these and though wow awesome, etc etc but then I checked the amp models and it's designed for guitarists, you may be able to get an acceptable bass tone out of it but I doubt it.
I bet the tuner still only goes to Low B, personally I'll be sticking with my M13