I would enjoy a long movie, but, if they really have to cut things, I won't mind TOO much if they stay true to the spirit of AF. I don't think that should be too much of a problem, since the books are relatively concise (if you compare to HP, for example).
Yes, the book is always better than the film, but why can't we just enjoy it in a different medium, nonetheless?
I agree with casting being the most important. I'd like most of the actors, not just Artemis' portrayer, to be not very well-known (at least, not very well-known in the US, where a lot of the movie action is).
I'd like an Irish cast as much as possible, humans AND fairies. Ireland's not that small; surely they can find many good actors there?