Denver problems
I actually flew out of DIA on the first day of operation and there was nothing like this level of disruption. Don't forget in that case they were opening an entirely new airport - 4 terminals on a different site to the old Stapleton - not just a new terminal on the same site as the existing operation.
As with most people I have avoided LHR unless there are NO practical alternatives. I guess from now on even impractical alternatives will become more attractive!