I went from Contax (with a Sinar back) to an H4D-40 last December, and I get my H5 this afternoon according to my dealer. I didn't fall in love with the H camera straight away, but now I'm happy with it.
Some things I noticed are:
-The mirror slap is horrendous. Set the mirror delay to 100ms and don't shoot below 1/125th handheld. Use mirror up for any still life work.
-400ISO is fine with the 40, maybe that means 200 for the non-microlensed chips. 800 is ok as long as you don't mind grain. The software's NR could be a little better but it has a nice filmic look.
-It's harder to focus manually with the Hassy compared to the Contax - don't know why, maybe it's the focussing screen, maybe the viewfinder, the lens characteristics, maybe I'm just getting old. I constantly back-focus. Ears sharp, eyes not, even at f8.
-The lenses aren't as good as the Contax regarding colour fringing. They are pretty much as sharp, but the software corrections don't remove all the green/magenta fringing around highlights at anything wider than f5.6. Lightroom will do it fine, so I bring my tiffs into LR for final tweaking sometimes.
-The camera has annoying little quirks regarding reliability. It tells me to reattach the lens, or the magazine at least once a day. Maybe I should have cleaned all the contacts with alcohol when I got it. We'll see how much better the H5 is. The lack of a vertical grip is a little annoying.
-The ability to customise the camera buttons is a real bonus.
-The software is good - not as good as C1 or Lightroom as far as features go, but it's reliable and produces great colour. I shoot tethered almost all the time. Forget about Lightroom for easy out-of-the-box colour - it sucks in my experience, even with Hassy's help creating a profile. It must be the LR 'color engine'
Test out a camera for yourself but don't expect to love it straight away. I don't expect the H5 to be very different at all. But nice paint job.
As you say, all IMO.