UPDATE: I studied the links above, and it appears the German Rohloff 14-speed internal hub addresses the issue of gearing range. However, the "ladder" (ie the steps between gears) may still be broader than in some derailleur combinations. The Shimano Alfine and Nexus internal hubs do not fare as well in the gear ratio department, having fewer gears. Nor do they accept a belt drive as well as the Rohloff, or quick release axles.
The articles confirm that these large hubs are very heavy, not surprising since they are totally packed with gearing, almost no empty space inside them, their weight close to a solid hunk of metal of the same outside dimensions. The frame makers who use these heavy hubs put them mainly on touring and urban commuter bikes, not in competition and other lightweight applications.
I could find no information on durability. It was my understanding that they do not have a long service life under heavy use, but that was before the newer Rohloff was developed. So for the moment the issue is unresolved for me.
But at the same time it should be noted that derailleur service life is not very great, either. The gear teeth wear quickly, especially on the rear cassette, along with the chain due to the shifting action, and due to offset forces when the chainring and cassette gear selection does not provide optimal chain alignment.
I did look at some Shimano Alfine-equipped commuter bikes a few years ago, but the bikes themselves did not meet my urban needs. Following a link above to Rodriquez custom bikes in Seattle looks promising, their commuter frames especially designed to exploit the Rohloff hub features. And they'll fit a Gates Centertrack carbon belt drive as an option, a low-maintenance, low-mess solution that appeals to me for a bike that gets parked in a condo. I'm going to research them some more.http://www.rodcycle.com