I've been following this thread, never responded because the OP inquired about long term durability and since I've only had the Nexus 8 for two months now I can't comment on that yet. Nor the riding in anger part. Anyway the derailer vs internal hubs debate has me intrigued. And I won't know where I stand untill I've had mine for at least a year.

With derailer systems I have a real problem with rusting on the front derailer, especially the clamp to the seat tube and the spring. It's where sweat from my face tends to drip on. The spring is not shielded enough to prevent getting wet, but just enough to prevent me from giving it a good cleaning.

Also I compared the gear range of my Nexus 8 hub with that of a hypothetical 8 speed rear derailer (based on my old hybrid's cassette). The Nexus's gear inch range is greater so one may have to figure a front derailer, extra crank ring and shifter into the comparison. But then once you add the FD set up, it's range is greater making an apples to apples comparison difficult.

Unlike man's free will vs determinism debate, which becomes moot with marriage, the derailer vs internal hub debate goes on.