My Alfine 8 makes me adopt a more relaxed style of riding, less frenetic acceleration and braking. You get really lazy about shifting down to stop, no need. It takes less mental capacity so you can pay more attention to the road or girls or whatever.
I did an oil bath after about 3 years, it was very clean inside but the oiled hub rolls easier and works down to lower temps.
In chosing a frame, you need a good method of chain tensioning.Simple horizontal dropouts, fancy sliding vertical dropouts or one of the more reliable, less creaky eccentric bottom brackets (EBB).
Most manufacturers assume that IGH users dont care about weight so put them on heavy bikes.