I don't check bags, I don't buy anything at duty free. On Monday (the 15th) the time it took me from walking out of the tube at Terminal 3 to being in the shopping mall where one waits for gate listings was 20 minutes. No line at the boarding pass machine, 10 minutes to get through security. This is typical of my Heathrow experience, but of course I dutifully allow the suggested hours just in case. My recollection is that the pre-September 11th security checks took a good bit longer.