Another way we leveraged open development was way before our playable alpha. We didn't have any maps yet, but we did have assets for making maps. So we released these props and textures, along with a document describing how to build a map and our barely-functional editor. Some of our pre-ordering folks started making maps right away. We asked the most promising community members to work on official maps for the game, for a share of the eventual revenue instead of our sparse cash. Without releasing our assets to our community, I'm not sure how we ever would've built our first map.
Head over and give it a read.