When Terminal 2 was opened at Heathrow most people agreed it is a great improvement over T3 which is largely replaced.  My main issue with T2 is that if you are flying from certain gates, you have to subterraneanly cross the runway – and therefore the time from the main terminal to the gate is 15 minutes or more.  I took after taking the very long escalator down under the airport on my way to the Singapore Airlines lounge.