I was just looking at the Shimano Nexus Cassette/Hub/Brake-contraption (
http://bike.shimano.com/comfort/Nexus/index.asp ) on Shimano's website and I'm wondering why these haven't caught on more for mountainbikes. It seems like it would be great to be able to remove the rear derailleur, put on a chain-tensioner and use the Nexus Hub. That way you could still shift the front rings, but wouldn't have to worry about a rear derailleur hangin' around waiting for a rock to tear it off. Are these things really unreliable or heavy or hard to maintain? I would love something like this if it was easy to setup and maintain (i.e. no limit screws and bodged shifts). Well, just wondering...