Just have to chime in and agree with this. The games went extremely well, amazing venues and all of that, but one of the best parts was probably invisible to those who weren't there. The city was empty (as empty as London could be, at least) so it was amazing time for visitors to see as much of the city as possible.
Same thing happened in LA 1984. Everyone was terrified of the traffic that the games would cause, but so many people took those couple of weeks off in response, it was like those who remained had the entire city to themselves.