While I've yet to get my IQ 180, the big dividing line for me is whether or not the just released live view would enable me to shoot with a tech camera without either a sliding back adapter or swapping the ground glass with the back. That is a line in the sand regarding tech camera use.
In the studio I can put my back on a Sinar camera and shoot tethered. I've tried the previous C1 live view option and found it unworkable...but in the studio I really don't care about the sliding back adapter which I use cause it works for still life images fine.
The question then becomes can the IQ 180 live view option eliminate the need for a sliding back adapter or ground glass in the field?
I don't mind using alternative methods of rough focus and framing...and I don't mind firing off a capture to "see" what I got. But, if live view as just recently released allows one to go into the field with the ability to fine tune framing and focus, then I see that as a benefit (combined with traditional viewfinders).
When shooting with the 645 camera, I don't think the live view will offer me too much. The focus mask is more useful. It's really a question of usability with tech cameras.