I'm a Gold Frequent flyer and regularly travel through Singapore. When I have more than 3 hours to kill I ALWAYS catch the subway into the city of if I'm pressed on time I pop into EXPO and pop into Changi City Point Mall. The subway is cheap, fast and reliable. Being out and about is better than sitting in a fake light lounge. I then pop back into the lounge before my onwards flight and have a shower and a drink before my flight.