My thoughts on IGH have really changed since I finally put together my Xtracycle conversion about four months ago.
Originally I thought I "had" to have IGH, but honestly in SoCal we don't get much sleet or snow (or rain for that matter) and my old beat 21spd Exage 500 drivetrain, well worn and abused, is actually working out just fine. It's also light, I've got it set up in friction shifting mode (one of the advantages of old school Deore thumb shifters I guess?) and works just fine for my (probably pretty modest) cargo bike requirements.
My wife's Breezer has a Nexus 8 redband and it's really nice, but honestly I think the gear range is a little limited for what I'd want on a true utility bike. When riding my X I'm towing our Wike kiddie trailer at least 90% of the time (it's our minivan substitute after all) and I really,
really like having the range afforded by a 21 speed drivetrain. I know there's some overlap and probably a Rohloff compares in an absolute sense, but I think even a 21 speed beats the range afforded by a Nexus 8.
So... to me, a properly-selected MTB triple with 9 or 10 speed cassette would be the most suitable, especially if the shifters spec'ed provide the option for friction shifting. Friction is way easy for me to deal with and while I guess it's not all that common anymore, it's a heck of a lot easier in terms of maintenance (set the endpoints and you're pretty much done). If my old lowend Exage is any indicator, anyways...
Just some thoughts from someone who had the opportunity to re-think the derailler solution
Steve