Singapore Changi Airport consistently tops the polls in passenger surveys. Here are some features that I like.
Free Internet Terminals
Free internet terminals, and plenty of them as well.
Laptop Desks
Work desks made for laptops with power supply, so no sitting on the floor next to a powerpoint that is meant for a vacuum cleaner. There was no wireless offered by the airport, but I had my mobile phone with me and I was sent a free access code by one of the local mobile phone services.
Transit Lounge
Very comfortable lounges. Just make sure you set an alarm as the temptation to doze off could be hard to resist if you are half way through a long flight.