I'm not a taper, but I have been loitering around these forums waiting for this very device to come along. So, as a musician, I'm happy.
I have one now, it turned up today, so I'm happy to try to answer any questions. The last Sound Devices unit I had was the original MixPre, (although I've also had a USBPre) so I'm not really familiar with the 10T or 6xx or 7xx line-up.
The two things I've noticed so far which aren't quite right
1) the reverb only works on projects at 44.1kHz and 48kHz.
2) the 'Main Outs' have the monitor signal routed to them at all times when the transport is in 'Stop'. This results in feedback through the monitors (unless you turn down all the output channels, or un-assign all the inputs, neither of which are feasible). There are lots of routing options for the headphones, and you can choose to send the HP mix to the Main Outs (XLRs and x1/x2 unbalalnced) independently and likewise you can send the Main Mix to the Headphones, so I can't see why it has been configured this way.
Dominic