It's an interesting look from a developer point of view. Compared to the power and speed of the relational engine, I think space savings are a minimal thing to worry about. Disk prices fall at a rate far beyond that of the improvements in CPU and memory when you compare price/performance.

I agree with many of the comments, that a well designed relational system is probably better, but this is an interesting solution and idea. If disk space matters a lot, perhaps it's worth considering, but I would recommend that you investigate some of the other suggestions first.