I can understand the ease of QNH for AT on scheduled ops but spare a thought for the other users who perhaps have to fly more circuits at different airfields than perhaps your average GA user. Having different altitudes to remember for each element of a circuit can be a nightmare and lead to eyes in the cockpit at the wrong time IMHO whilst looking up the altitudes to be flown.
No, sorry, I don't buy this one. I actually fly lots of circuits at lots of different airfields when I'm working. I'm not exactly ETPS standard (far from it), yet I still manage to keep up with lots of different circuit altitudes.
And as for flying in close proximity to lots of different airfields, all with different threshold elevations, I'd say it's even more important to fly with QNH set. Makes coordination and traffic awareness just so much easier when everyone's flying with the same altimeter setting.
Flying with QNH set, as R Scandal points out, does make you much more terrain-aware.