In terms of the new edition: As someone who has seen Hackmaster around but never actually purchased it, here's my list of some conceptions and misconceptions that get generated in the mind of a potential purchaser:
1) I don't happen to go to game stores frequently, so I don't see much of the inside of books I buy on the net. Result: very cautious buyer. That's probably not something a new edition can change much, but there are probably ways (see later points) to make more sales to internet-only buyers.
2) Not knowing what's needed to play. I assume from AD&D that one needs a PHB, MM, and DMG. That may not be the case, and if not, the information's not out there "in my face" enough to make me scour the websites to find out. The initial investment required for three hardback books all at once is higher than I'm willing to pay for an experimental perusal. [edit: Another thing I just thought of - I've assumed the books are still hardbacks - that is what I've seen in stores when I saw HM books the times I've been in stores. It only just this second occurred to me that there might be a softcover option.]
3) Not knowing what's going to be usable in the books in a DIFFERENT game if it turns out I don't want to actually play HM. General utility, even if it's just ideas, is sort of a backup value. If I don't want to play the game, I at least don't feel stupid for having spent the money.
4) Perception on the net that HM is highly complex. Potential buyer frightened off by the idea that the game is designed to be unplayable without lots of work. Some sort of damage control on this perception would go a long way. Whatever damage control on this might already be out there hasn't "hit" me out of nowhere in the course of internet browsing.
5) What I've seen of HM looks like a hell of a lot of fun. The pure-fun hack and slash portrayal I think is a fantastic attraction. That's what has kept me sort of at the edge of buying a PHB rather than just making a "won't ever buy" decision and moving on, as I do with most possible purchases. I wouldn't change that marketing image in a new edition (though I assume you won't be able to use the "Demon god idol" on the cover any more).
6) Also, the parody side of things doesn't turn me off when I read about it, except that I worry it will be too intrusive or make things too complex. Light parody actually appeals to me. Intrusive parody, though, is the concern - not nearly as big a concern as the other ones listed here.
7) I've seen that at one point you were giving away PHBs, or offering them at a deep discount. That strategy is one that would allay a lot of my buying concerns (obviously). I think a free basic "play almost immediately" pdf would also help. I happened to miss the free offer, but even reading the thread about it brought me to the HM site. If there'd been a free pdf (there might be, I just didn't see it) I would definitely have downloaded it. Normally when I download a pdf I don't do much with it, because I hate pdfs, but if I wanted to get my group started on HM, it's good to have something for the players to download without spending money up front. This worked for a trial attempt on C&C (failed, but players enjoyed it enough to buy a couple of copies of the books before the editing problems in the C&C 1st printing pissed them off so much they started to make fun of the game itself). Point being, though, the DM being able to say "Let's try it out - just download these quick-start rules" goes a long way toward getting the game onto a table and later purchased.
8) Can't think of anything else. Hope this helps as a profile of the "almost buyer." It's worth mentioning that on a single government salary with kids, I probably don't have the gaming budget of most 39 year old players, and that probably puts me outside the profile of your ideal customer base. Still, I think these points probably apply to lots of other people, just with a lower threshhold for making the jump to actually spending money.
Edit: also, the fact that a new edition is coming out at some point is a problem, too, at this point. I assume (whether correctly or incorrectly) that if I buy the current edition it will be superceded. As a 1e player, I'm already really tired of being in that boat. Since that news is now out, you probably ought to start telling fans what to do about it and how to think about it.
