If departure is after KLIA Express (train) starts to operate then staying at KL Sentral at either Hilton or Le Meridien is a great option ... very nice 5-star hotels that are connected to the train station (bellhop will carry your luggage if you wish) and 30 min train trip to KLIA. Much nicer than staying by the airport but only works if your flight is after 7am as first train arrives at 5:30am.