I would LOVE fan filters (for my HAF 932), as well as a lot of other people I think. I'm on a lot of forums, and there's always people complaining about dust problems, and always speculating on whether to get a HAF 932 or not because they don't want to clean it out so often. I really hope they get released as I think it's a great idea, especially if they really do decrease air movement by a mere 3 CFM.
And I don't think this idea is getting enough exposure. I'm pretty sure EVERYONE w/ a HAF would like to voice out their desire for some of these, not just those in these forums.