About a year ago, I was accumulating parts to build up another touring bike. At that time I researched parts and decided to use an older XT hub (M760) because it had a steel axle. In my research I noticed that Surly was using an older steel axle on their Big Dummy cargo bike and the newer aluminum axle on their LHT. Presumably the cargo bike needs a better hub, so I took that as an endorsement for the older design, thus I avoided the newer (M770) rear hub.
There is a lot more discussion at this link, it is on recent (M770) rear XT hub issues on a forum for Long Haul Trucker owners. On that forum I am known as Loaded Tourist in Madison
http://groups.google.com/group/surly...37f23f2a2b554d
Surly 2011 catalog lists Deore as the current rear hub used for the Big Dummy cargo bike.