OK, I'll be devil's advocate here! I absolutely adore my DP6. It's actually effective with the 5D3, as opposed to the 5D2 which would lose all that glorious resolution as soon as you hit record.
Focus assist is fantastic in some situations - but frankly, half the time you really don't need it because the monitor's resolution is so good.
Question for you other guys - are you not putting the DP6 into DSLR Rec Mode? Because turning it off to frame a shot sounds totally unnecessary to me. I hadn't noticed edges being cut off in DSLR Rec Mode, after you hit info - will check that tonight - but even if it does cut off a tiny bit, why not just hit Info on the camera, to get the windowed picture, instead of turning off the monitor?
Frankly, for the kind of shooting I do much of the time, I just couldn't use a ZFinder. A director looking over my shoulder can see exactly what I'm getting, and we don't have to stop between every setup for him to review the shots. He knows if it was a good take before he even says "cut", and we just move the heck on. Or, for example, have you ever tried to keep your head pressed up against a camera through a dolly/slider shot? A monitor with an articulating arm is the only way to really take advantage of a DSLR's tiny form factor, and put it in some weird/interesting places