A month after getting my new bike I'm a thorough convert to hub gears. Not only are they wonderfully smooth in use and pretty much sealed against the crud that comes off the path, but -- as I discovered today -- they are also a dream to adjust.
New bikes tend to need a bit of tightening up after a few weeks of use and settling in. Cables stretch and fixings loosen, and you find that gears start to drift out of correct adjustment. The Shimano Nexus is no exception, and on my last journey, I found that third gear wouldn't stay in gear, and a few of the others were a bit tricky. I was anticipating the greasy, time-consuming horror which is gear adjustment when you have derailleur gears. I've always found that you spend hours patiently adjusting screws back and forth, only to find that if you get the bottom of the range right, the top is out, and vice versa. It's like a bike equivalent of the 'Right Said Fred' piano moving experiment.
In contrast, the adjustment process with the Shimano Nexus is absurdly easy. There's a little windowon the upper surface (and on the lower surface, in case you've got the bike upside down) of the hub which shows you two vertical yellow lines. When you're in fourth gear, the lines should meet. If they don't (mine didn't), it needs adjustment. All you do is rotate a knurled collar where the gear cable enters the twist grip shifter on the handlebars until the yellow lines align -- no tools required! A quick flip to first gear then back to fourth allows you to check that the lines are still aligned and tweak if necessary, and that's it. It's an entirely non-greasy, easy, two-minute job, and everything is back to smooth efficiency afterwards. I think I'm in love with a hub gear.