For me, I'm pretty vehemently opposed to the design document approach. Why? Because it leads to derivative work. Or stuff that sounds good on paper, but then really stinks in practice.
For Arcen, what we practice is evolutionary game development -- where we try exploratory ideas that we have a strong feeling will improve things, and then see how it works out.
Note that it's not a democratic or crowdsourced process: if a bunch of new people come on and make a lot of really silly suggestions that are counter to what the game is and what we want it to be, we'll politely decline those suggestions. Even if those suggestions would be a great game, if they aren't in keeping with the overall design goals for AVWW then they don't fit. Suggesting features that would be appropriate for a serious racing sim to the Mario Kart developers should get you the same treatment, if you see what I mean.
If the worry is that there's nobody steering the ship, that's something that I think you don't have to fear. I, personally, am steering the ship. The thing is, I just don't have a particular preference for my own ideas over the ideas that are presented by other people, so lots of people get to participate and what seem to be the best ideas to me at the time get implemented. That's not a perfect process, obviously, but it's not the massive stew-pot of unpredictability that you might think.
Now -- has the game been undergoing some radical changes post-1.0? Yes. I think the reason for that has been rather the same reasoning behind why AI War changed so much between 3.x and 4.x. Basically, there was a strong core there, but there were a lot of nits. And with a suddenly-larger playerbase, we suddenly had a new perspective on the nits and could do something about it. We also had more brains generating potential solutions to the nits as the community grew in both cases, and so better solutions were arrived at more quickly.
With 1.3 (and beyond), honestly I don't plan any major overhauls. I mean, if we find out there is a need for something then obviously we won't let something that stinks stay. But I think that the current systems are quite good and really allow for expansion. What I want to see in 1.3 is more content development, more things that make the world feel like a living place, more things that make use of the new citybuilding/NPC underlying mechancis, more stuff that makes use of the environmental threat mechanics, infestation mechanics, etc. Plus more spells, more spell modifiers to make more procedural spells, more enemies, more procedural modifiers to bosses in particular to make them more unique, and so forth.
And then there's the question of the art style. That's been so divisive, that, given the financial chance to do so, we're going to explore changing it. Nothing may come of it, or we might have something that a lot of people find more palatable. The stuff from Studio G is looking particularly promising lately, as it most keeps to the spirit of the existing style/mood while looking amazingly better.
Anyhow, to sum up: I firmly believe that the best ideas can't be thought up in advance. If you want to make a big-budget game that isn't all that innovative except in one small area or perhaps which has a really cool story, then by all means go with the design document approach. If you have a staff of hundreds, that's basically required in order to get anything done. But that's not what we do: for better or for worse, there's no other game like AVWW out there, and our exploratory design process let's us gradually chip away at it until it looks more and more like what we didn't even realize we wanted it to be. That's a nontraditional process, to be sure, but I think that's the only way to have a lot of innovation in one game rather than having something that is an incremental improvement over past games.
For a lot more details about our process, see:
http://christophermpark.blogspot.com/2009/10/iterative-game-design-right-way.htmland
http://christophermpark.blogspot.com/2011/06/more-musings-on-iterative-game-design.htmlAll that said, I understand the core concern that is here. I can see how this process could be incompatible with some people and their expectations or goals. If that's the case, then I'd recommend waiting until the game settles more, and then buy it then if it seems like something you would like. I'm not offended by the idea that someone might choose to do that, and I can even relate to the reasons why you might do so. But we're not doing things the way we are because we're just flailing or have no idea what we're about: we're very directed in our rapid prototyping, and have a very specific process for it.
Hope that helps clear it up a bit at least!