I find IGH good for extremely cold conditions, when RD cables and the pulley wheels would freeze up.
For all other purposes, 6 to 8 speed RDs are practically bomb proof, cheap. Easier to service as well. Also, 0 slipping on climbs, unlike many IGH.
Another disadvantage is when taking a wheel off to fix a flat - it is more hassle with an IGH. Bike shops in my city charte 2 to 3 times the price for changing a tyre on an IGH wheel - I'm sure they're skilled enough, so it's just the matter of extra time/hassle.