Although I've been curious to have a look at Death Forst Doom and Jim Raggi's various other adventure modules, I didn't really see the point of releasing your own version of "the game." Of course anyone who deliberates for more than a year over a $5 purchase is probably not part of anyone's target market, and my reasons are unfairly contradictory, but here they are, supported by my recent experience in playing in a "LotFP" game.
My first point, is the doing "weird fantasy" is a worthwhile goal, but it's not supported by new rules. I think it's best supported by adventures (and Raggi's adventures have been very well-received) or you do it by playing the game with people who have all read Lovecraft or whoever and agree that's the kind of flavor you're all going for. Or a little of both or a lot of both. Yesterday's game might be called a little of both and in fact that made for a great game. The referee had the LotFP pdfs and had created his own adventure. Speaking for myself, I had a vague understanding of what "weird fantasy" means and I was ready to participate. The other players knew at least as much as me.
Our characters were caravan guards and our patrons had chosen a bad route, and gotten us lost, so we stopped in a little village to ask for directions. It was a decidely creepy village, but most of the caravan members wanted to sleep in a warm bed rather than in the open. We were attacked at the inn, captured one of our attackers, and learned that the villagers were all part of an evil cult that met in a cave outside town, led by the obviously creepy mayor. We went out to the cave, killed the leader and most of the cultists and got killed ourselves. And again, it was great-- it's a nice variation on the usual low-level adventure theme that the little village in need of your help wants to throw you into a fissure. And that even though you know you shouldn't be there at all, for some reason you feel compelled to stay. But I don't think Raggi's rules had much to do with it. There are some nice innovations, some of them borrowed from recent editin. Ascending armor class makes a lot of sense-- you should just have to roll higher than the AC on a d20! Obvious but ingenious. His encumbrance rules are great, too. Most items, other than metal weapons or big weapons "count" more or less the same, and every 6 items you move to the next lowest encumbrance class. I'd like to start using encumbrance and this would be a good way to do it. Magic-users can use swords-- they're just not that great at it. This is a really nice improvement-- no more master of the dagger. And no more guessing someone's character class by checking out what weapons and armor they have. But none of this really contributes to weird fantasy flavor. They're just nice and relatively minor innovations on the rules. (And maybe part of what's nice is exactly that they are minor.)
My other point is kind of unfair: even if you can re-create the ruleset to encourage weird fantasy, you shouldn't. In these rules, both Elves and Magic-Users are Chaotic. This changes and complicates usual understandings of all three of these entities. Elves and Magic-Users are more decidedly weird. And Chaotic is not such a simple short-hand for evil. The magic-user and elf definitely had fun with this and it added something to our game. But adding new *permanent* limitations doesn't add to "the game." Because what I most appreciate about D&D is its versatility. A campaign where magic-users are required to be chaotic is cool. But so is a campaign where Magic-Users are required to be lawful because magic is powered by increasingly inflexible adherence to a higher order. What's the point of hard-coding such innovations into the game rules? Choosing one option always requires foreclosing others, but rather than do this at the "game system" level, let's do it at the campaign, setting, or adventure level.