Lots of opinions on them.
1 fact is that when the rear dif is locked, both rear wheels will move at the same speed. This is fine if you are going in a straight line. When you turn(with the dif unlocked) the inner wheel will not rotate as quickly as the outer wheel. But with the rear dif locked both wheels rotate at the same speed, which is fine on ice or any slippery surface, but on dry pavement this will put stress on the dif and the tires, potentially causing major damage.
Rear dif locks for off roading are common and have their uses. Unless you are going off road I dont see the need to use them. If you are concerned about winter driving on paved roads I'd recommend either getting an AWD denali or a 4wd tahoe.