From the beginning of this month – November 2016 – the Malaysian government has tightened rules on duty-free purchases in Langkawi and other duty-free islands.
As a resident in Langkawi, or as a visitor, it is now less attractive. You are restricted in the volume you can purchase, and where you can purchase duty-free. It appears, for example, that eating at a restaurant you will have to pay duty for wine etc. with your meal. If you want to use a car you have purchased duty-free on the island on the mainland you will have to pay a very high bond, apparently.
Overall, apart from making me less likely to visit Langkawi again, it doesn’t really affect me, living in Penang as I do. If you think it might affect you please check yourself, as I have only briefly read about it and don’t know the complete details.