Interesting (and challenging) discussion guys. The one essence of poker that many players forget is making notes about other players, and therefore why shouldn't a HUD be used if you think it helps with note taking! Though I agree to some extent on the fairness argument, cos you don't get that in live poker as opposed to online, however, people still take and make notes, so we have to accept that life goes on.
Think about it. If you have a job and you have certain tasks or appointments, you may well make notes about them, as it could affect your job performance if you get them wrong. You may also need to report on the performance of another person or a piece of equipment . Without your notes you may come unstuck. Why not do that in poker? It's not just a game. To some and many people it is a job and a way of making some (sometime serious) money.
Take poker seriously, make notes and get better not just complain about others having a competitive edge.