The idea is to put the iPad in a hinged case that contain a bluetooth keyboard to use for typing instead of the on-screen keyboard. This essentially turn the iPad in some sort of disfunctional netbook (try to use a netbook without a mouse/trackpad).
Sure it would be nice to use to type long documents but does one really need to use an iPad for this? Long document typing is better done on a full feature computer.
The iPad is mostly oriented for casual document writing, email, surfing, gaming an a bunch of other portable application usage. I don’t see it being a good document writing platform for day long usage.
I think the case look good but will not be really practical.