I have 10,000 all weather miles on my Kettler Silverstar. The Nexus hub has been dead reliable, requireing only a yearly regreasing. Chain life is over 5,000 miles, with cleaning/lubrication only 3-4 times per year. The hub is silent except for the freewheel, which makes the usual faint sound. If you buy a bike with a noisy hub, it is clearly defective. I commuted 3 years and 7,500 miles on a derailleur bike. The maintenance required was just crazy, and I still had failures. Personally, I would not consider anything but an internal hub for commuting. Ditto for hub brakes and a hub dynamo.

Drawbacks: there is a slight friction loss. I don't notice it, but some people do, and it bothers some of them. It is a subjective issue, not a utility one. A potential realproblem it that the range in gear ratios is about 1 - 3. That means that there are no "granny gears" for spinning up really steep hills. That might be an issue in San Francisco, but not here in the DC area. The third potential drawback is that the Nexus is not intended for offroad use -- jumps and rocks. For normal riding, that is also no problem. The Rohloff 14 speed hub has a very wide gear range and works sell off road.

I think it really comes down to how much you like the feel. If you like the feel of riding it, then buy it.

Paul