Another simple and timely idea...
The independent network of (780 home-based) travel-agents, Travel Counsellors, has set up a really useful website to monitor the experience of passengers at UK airports.
UK Airport Delays enables air passengers to simply record the time they spent queueing at their airport, and produces league tables of the best/worst airports.
Needless to say Stansted, Heathrow and Gatwick were occupying the bottom three slots on the table when I looked today. But, newly launched with only 178 entries so far, it's hardly a reliable evaluation. Wouldn't it be useful though, if the site was widely publicised and thousands of air passengers started reporting each week?
Of course, the tendency will be for people to use it when they have had a bad experience (to 'get it off their chest') so the computed average delay times themselves will hardly be 'balanced' data, but the relationships between like-for-like airports will be interesting.