Captain Planet->It's not the amount that's being charged, but the way it is being collected that makes people unhappy.
A number of years ago, I ran into this situation at Vancouver International where they had a similar airport improvement fee. I had spent almost all my Canadian dollars. My credit card was at it's limit and suddenly I had to pay C$20. I had to run to a bureau de change to change 20 pounds into canadian dollars (the commission was ridiculous) just to get out out of the country.
Now, I don't remember the travel agent mentioning it when I booked the ticket and I don't think I ever saw written down terms and conditions.
If the fee is so small and so justifiable, why isn't it included in the general airport charges?