Never done it, but would LOVE to hear your adventures if you do get involved with one of these =)

They are quite astounding, and really good for building up neighbourly relationships and a real sense of community. Also, many works that you can't actually perform for yourself are a lot cheaper with these as they are so close together - ie, concrete slab pouring. Where you pay a massive premium just to have the concretors show up on site, you only pay that premium once and pour multiple slabs. Massive savings. Works with many of the trades. So you end up with a beautiful house for basically the cost of the land + supplies, very little of the costs of having it built. BRILLIANT idea.