I was fetching my parents from the airport but for once in my life arrived at the airport early. So decided to check out the Viewing Gallery at KLIA. It's actually been there since the airport opened back in 1998 but I've never actually been there.
At the Departure hall of the Main Terminal Building, you just keep walking straight into the airport, past the Old Town Coffee House, and there's a corridor that leads you in. You get to walk above the immigration area and the Duty Free Shops of the Contact Pier. The Viewing Galery itself is located directly above the aerotrain station. It's also where the Muslim Prayer Room (Surau) is located.
Despite rumors of the gallery being closed, I managed to get to it without any hindrance. The air conditioning there is not that great so if you're spending some time there you will want to dress lightly. Most of the people there were killing time, although you could tell who were the Professionals from their SLR gear and most importantly the spray bottle of Window Cleaner they were armed with.
From here you get a pretty good view of the East and West wings of the Contact Pier, the Aerotrain, the Northern side of Satellite A, and Runway 14R and 32R.
I also got a video of this "ajinomoto" plane (9M-MSG !)
Incidentally, KLIA2 also has a "Viewing Gallery" of sorts ... they are to the left and right of the Main Terminal Entrance, so you only get a view of the stands on the northern side of the Main Terminal 2 (next to the main road).