I had a power lok installed in the rear diff in my truck last fall, and I absolutely love it. Originally my truck's rear diff was open, and I was always having to go into 4wd to get anywhere in winter.
Before I had it installed I was dead set on getting a detroit locker. The thing that changed my mind is that I do much more long-distance driving than off-road driving, and the extra tire wear of the locker made the difference. For me, the noise and different driving characteristics wouldn't be a big deal. My truck being an auto, and with it's longer wheel base (club cab, full length bed), the harshness would be dampened quite a bit.
About the only other thing that might be useful to someone considering a locker vs. limited slip that I haven't seen mentioned in this thread yet is that if you do go off-road with a clutch type limited slip and you happen to get one wheel up in the air, you may end up burning out the limited slip very quickly if the angle is such that the fluid all flows out of the diff and into the axle tube of the wheel that's still on the ground. With a locker, if you find yourself in that situation, it's just not an issue.
Mike