From all appearances, the 2005 and newer Ford Superduty hubs fail a lot less than the older ones. They also seem to fail in the locked position, which is much less fatal.
Nonetheless, I've had a hard time with the passenger side one for a while now. This past Sunday I could not get the drivers side one unlocked at all after 20 miles of rocky road (a couple miles of which might qualify as trail).
What I did know is that my van doesn't track as nicely as it usually does with one of the hubs locked. This made for a bit more work on the drive home than I really wanted. It also costs about 1mpg (not that big a deal for one trip). What I didn't know is that I could have just pulled the locking hub out and driven without it. Three screws on the face, and then some pliers to pull it out by the standoff tabs. Super easy.
The failure seems to be in the plastic carrier no longer grabbing the gear that slides in and out of position. I sort of wonder if I could have just gotten one of those from Ford, but I didn't find a part # in the vehicle diagrams. (There might be a rebuild kit?).
Two entire hubs from Ford were very similar money to a set of aftermarket hubs that Warn started shipping earlier this year. The Warn hubs come with a lifetime warranty, so I went that route.
The Warn hubs are almost entirely metal, save for a large spring retainer that could possibly be left out. They look like they would fail in the unlocked position if the cap/dial was damaged. The more likely failure mode seems that the wavy spring goes limp, in which case they'd fail locked (but could be pulled).