V, I think the commentary of Shaun is worth listening to compared to other commentaries which I have found to be
It was the first one I listened to more than once and the first one that gave me any interesting insight into the film. YMMV. Can you tell I'm nervous in case I over-egged it?
My opinion that the DVDs are worth buying simply for the commentaries mostly applies to tLoG though. Four very funny men with unusual senses of humour and sources of inspration I had never heard of (I've looked many of them up, believe me) in a room with some water and a playback. They go very slightly insane and some of their best lines are in the commentary. It doesn't really translate. An impression of Mr Kipling. Reece saying "Look at that cat!" Jeremy saying, "And the rest!" or doing an impression of a chainsaw in the distance. Made me weep with laughter when I first heard it.
Back to Shaun - if you already have it you have nothing to lose. I enjoyed the first two commentaries. But the second is more luvvie. Pegg & Wright are a great team.