Departed from T3 early morning (Air Canada) and arrived back early morning. I frequently use T1 and T5 and have very positive opinions on the arrival experience - generally very fast and smooth with the exception of T5 when BA flights can't find a gate to park. T3 has improved significantly. The building is still very old and the departure hall is still like a third world airport. However it is not as crowded as it used to be not a long queue in front of security. Some annoying passengers questioned why they had to take off their accessories water etc but you encounter those kind of passengers everywhere in the world. After security there are plenty of shopping. Heathrow is probably the best place for airport shopping partly due to the exchange rate. Arrival was a good experience. Its a long walk as usual but for EU/UK passport holder or those using Iris scan there was no queue at all. You whip through immigration in a second. Then the luggage came out before I even arrived at the belt.