It actually says 15-20% premium on regular JW Black which even though would not be a huge amount extra it does sound a bit rich at the same time (excuse the pun). But I think I'd at least buy one just to try but will not be going out of my way to get one.
Having a JW blue currently which is actually very good with an brilliant and long finish. Not sure if it's worth the full bottle money though. (Mine is from a 4 pack of 200ml bottles which I think is very good value)
I don't see the magic. If you want a more smoky Walker, pick the green. Black is great, if you want it smooth and easy. Red is great if you want it rough and cheap. Haven't tasted the gold and blue yet.