i don't know if this is the style you're looking for, but i have a Scott SUB 10 men. alfine 8 IGH, hydraulic disc brakes, and a styling that, to me anyway, doesn't look to have that
"hybrid grandpa style", the orange is a bit flashy though. it's on sale at REI for $970 bucks right now.
here's mine:
i was also considering a Kona Dr. Fine (a similar IGH/disc brake hybrid), but availability and cost led me to choose the Scott.
as for IGH disadvantages, the two biggies are weight and added difficulty to remove the rear wheel to fix flats, but honestly, if you just practice removing the cable a few times at home, it's really not a big deal at all unless you're totally mechanically inept.