In seriousness, the significance of the stones depends a bit on whether they were dragged from the Preselis, or just lay littered around Salisbury Plain. If it was the former then they could have had amazing ritualistic power. If it was the latter then the significance might also have been great, but convenience could also have played a part in their choice.
In situ it has to be said that, although the colour of the bluestone is rather pleasant, they're not exactly in the same league as Lewisian Gneiss. It's a different story when you put them in context though. Carn Meini in the mist is an image far flung from the theme park that Stonehenge has become. I'd like to think they're Welsh!