I don't have any experience with IGH but I don't see them as being any more durable than a derailer system nor are derailer systems all that delicate. The derailer systems on my touring bike, including the STI shifters, has 9000 miles on it, including 5 tours and I've never experienced any problems with it. My commuting bike has over 12,000 miles of summer and winter riding on a derailer system with STI and, again, has had zero issues. I have a mountain bike derailer system with over 5000 miles of hard off-road (including a few crashes) and winter commuting that is going strong as well. I've owned 35 derailer bikes total and can't really say that any one of them has every "failed". I had a shifter cable blowout once but that's the extent of my "troubles" and that could happen with any system that uses a shifter.

mdithey does make a cogent point, however, about IGH. I doubt that you could walk into Ride On Bikes in Lewiston, Idaho and get the parts needed to fix an IGH of any flavor if something when wrong. If I screwed up a derailer, I could walk into any shop from Ride On Bikes to Ride 'n' Slide Sports in Beckley, WV and walk out with something that will get me down the road.