I had a "fashion style" commercial campaign that needed high res, we were shooting 2 options plus a series of 6 for magazine usage, which needed lower resolution.
I got to shoot the IQ 280 on a DF+ body and although is kind of recursive I'd like to share my experience.
Note: I had shot before with hasselblad 22, 39 mpix and was quite happy but never liked phocus and last year I did a quick test on a personal shoot with a friend's h4D40 and switched back to canon (5d2/3) because I'm used to Capture One workflow and color and hasselblad + Lightroom seemed clunky and flat.
First of all, i shoot tripod 99% of the time so no problem about weight. Ergonomics are OK and in 5 minutes you are up and running with menus and all, very nice and intuitive.
Settings and DOF: I was shooting 2 pictures, one in which I needed medium to shallow DOF and other with a little more, in canon that would have meant 50 1.4 @ 5.6 and 8, 100 ISO 1/200, so I went with the 80 2.8 @ 8 and 11 50 ISO 1/200.
So... to get similar results you need 4 times more light, sometimes this is overseen but in most of my shoot I'm OK with 4 500W D1 and 2 D1 1000 and normally don't get used at full power, in this shoot we had a mix of 2400W 7a and 8a and were close to high most of the time. I suppose that going to 100 ISO or 200 would be OK in terms of quality but having the wattage who cares!
Focus and general shooting workflow: I found focus to be pseudo quick and very accurate, with the known "issue" of being only central point, in this case it didn't bother because it was a very specific picture pre framed and pre focused so just had to confirm focus in the computer as we were shooting tethered.
Speaking of shooting tethered, great experience, better than canon even with four times the pixel, very impressed in transfer speed although we were shooting to a beefed up 15 macbook pro + external display that sometimes struggled to keep up, but overall experience was smooth with no crashes, problems or lockups.
So to wrap up the experience, very good, a little slower than used to with the canons but fine and the files are great (more on that later) but the other six pictures in which we had to shoot from 200 to 400 ISO, 2.8 to 4 and 50 to 80 to mix ambient light with small touches of flash (profoto B1s are a winner for that jobs by the way) were shot with my good old 5d3
Retouching and file management: Ok, here starts my love-hate relationship... files are absolutely great. Hands down the best files I've ever worked, the level of detail is ridiculous to the point of retouching a single hair crossing the ear on a full body shot or being able to count the eyelashes. Capture one does a really good job on pulling all this and working or exporting doesn't take much longer than 22mp files in my old trusty 2010 imac (i7, SSD, 24 GB RAM) but once you start working the file with all the color corrections, masks and multiple layers file size starts to grow... save times increase and I realized for the first time in 4 years that my imac wasn't enough for this file size, which is normal after all a 4 year old "amateur" machine is working a top of the line back file. After some grunting I could finish and the results are excellent.
So, to summarize: Files are great, detail is awesome and the workflow is slow but very well rounded. BUT working with this camera-back means that all the equipment has to be up to the challenge, you'll need big lights and a lot of computer power.
Will I consider buying one of these? Absolutely! just put one extra zero in every check and I'd get one!
Jokes aside if it's needed and paid for enough I'd be more than happy to own one of these puppies, but for me is a work took and has to make financial sense.
I'm curious to test the IQ 250 that can be shot more like a DSLR and won't be so light and computer extreme to use.
I hope you enjoyed the reading and sorry about my english... not my first language and haven't written for a long time.
George.