I use a silk liner and would agree with all of the advantages mentioned by Humph and his predecessors above, except to say that I don't feel they add as much in terms of warmth as Humph thinks they do, but then I'm a specially shivery, miserably cold type of individual.
On the downside, they try to strangle you in the night and will entangle your legs do that any emergency evacuations when Mr Bladder comes to call will be fraught with danger, specially late at night in Braemar. The Death Bladder Dance amongst other people's guy ropes is not just a Highland Legend, it truly does happen.
Otherwise, you may think you are free from the clinging beast but will have hobbled to the Gents and back with a silken shroud floating from the back of your undies like some ghoulish wedding train.
Apart from that, they're great. Mine is full of loose change, elastoplasts and old toenails