Re: Fun with MF images, part 2: What are you shooting with that MF back?
Ooo, I get to reply first!
All of those things you mention are true. DoF is slim at best (a plus for me), there is noise at higher ISO (though the 30+ really makes a usable 1600 for me), and the AF is slowish.
That said, I sold my Canon 1DsIII and my 5D... my Phamiya with P30+ is my main and only camera (aside from a small P&S). So far it hasn't let me down. I will be bringing it traveling, I walk with it frequently, and take family images, etc.
The speed is definitely a notch down from using a 35mm DSLR, but it depends on what level of compromise you're willing to accept, and whether that compromise includes a big bulky clunky camera slowing you down vs. vastly improved image quality?
For me, the 30+ is my main everyday camera. It sits in a photo backpack behind me, ready to roll. I've taken it hiking with my pano head (heavy, sure, but other than, a joy). I've taken many family shots with it, handheld. I've taken regular stupid snapshots with it. I've shot it handheld while walking around a farm festival thingy with my son and fiancee. There is a bit of a learning curve (learning how to handle the weight, predict your shooting opps a bit better since things are slower and more deliberate, and dealing with carrying a tripod when you want the best image and/or the light is low, etc.)
So far I have no regrets.