It's funny how we all can have such different experiences.
In the year+ that I've been lurking I've read the stories of painful experiences at LHR. In my 2-4 trips/year for the past 3-4 years through LHR I've never had a problem; I'd even praise the UAL staff there for their speed and willingness to help (especially in often switching me from LHR-IAD-SFO to the non-stop LHR-SFO). On these trips I'm usually flying on some type of coach fare with a confirmed mileage or SWU upgrade.
My only complaint about my LHR travel is the recent lack of 747-400's. Business on 777's is more than adequate, but upper deck on a 400 is so nice...
-BP