I don't care for them but its not the dog, its the coat. They just look too fluffy to me. Its purely a "look" thing (in the same way I prefer sables over blankets or solids) and has nothing to do with the dog or its abilities.
That said, I've known some wonderful plush/lc GSDs, and if one fell in my lap I probably wouldn't say no, but I wouldn't seek one out. I can't imagine the hair, yikes!