I have been in Malaysia 3 years ago. It was with a tour operator and I paid 1750 euro for 19 days, flights included, spending 3 days in KL and the rest in Langkawi. Very nice hotels.
In Langkawi I have staid in Sheraton Beach Hotel
http://www.starwood.com/sheraton/sea...propertyID=281
Langkawi is more savage than Phuket, as there are less tourists. I dont remember a European tourist there. many people from Sngapore, Korea and may be some Australians.
We can see a lot of monkeys, exotic birds, etc evreywhere in the hotel, on the road, on the beach.
I dont like too much Malaysian food and I ate almost everyday Chines food. They say that they can also make Thai food, but it's really different, they just make chinese food a little bit spicy. So I was a little bit disappointed because I like real Thai food.
It was a nice trip, very quiet and it's possible to make a lot of trips around the island.
Diffeent people too. langkawai is mostly muslim. very friendly but I dont think you will find a hot nightlife there. As I was still with my Belgian GF, I didn't look for it.
Nice country, I am happy to have been there, but I definitively love Thailand.
I know it's possible to take a boat from Langkawi to Phuket, but I dont remember the rates and I am not sure it's possible to get a one way ticket.
Hope this helps