The gas works images don't seem to be as amazingly immersive as the ex-salt mine in Les Baux (which I think is the original locale for this type of show). I will be seeing the one in Bordeaux next year. Each year they feature different artists, so it's something you can keep going back to if you enjoy it.
It isn't the same as seeing the originals in a museum, but if the museums are crowded (as they often are around these masterpieces) you can't really appreciate the art work there either.
[I'm just back from a very interesting lecture on Turner and Constable at our local library. Slides of paintings projected on a movie screen are not much like the originals, except that the lecturer had high-res close-ups to illustrate his points about the painter's technique and you really could see the brush work and impasto that way. It would be nice to visit the museums in London without the public!]