Many fly-ins do not charge a langing fee. Well guess what - I'm quite happy to pay a standard landing fee for the airfield concerned and if the airfield waives the charges would be happy to pay the same to enhance the fly-in experience. What I'm not prepared to do is pay some trumped up excessive fee for the honour of walking round a trade stalls and being able to use a few plastic porta-loos (I guess that rules out the PFA rally for me then!).
What I hope for is a friendly atmosphere without too much officialdom (I like to walk around and look at the other a/c, don't like cadets telling me where I can walk, don't like yellow jackets), catering at a fair price, appropriate aviating facilities (met, etc), and reasonably efficient handling (i.e. marshalling, ATC/FIS/Radio) whilst aviating.
Furthermore, no slots thankyou (club a/c availability can just be too unpredictable sometimes), and no departure or arrival windows / restrictions (sometimes I need to take the club a/c back outside of your departure window). I can live with doing the PPR thing, but don't ask for it days in advance as I can't always tell which a/c I'm going to be using.