Looks like a very nice device. Assuming the software has search capabilities and the ability to have several documents loaded at once (I don't think anyone knows that yet?) it would be great for table-top role-playing GMs. This is probably not a market they've even considered, but most RPGs are available as PDFs these days, and it beats carrying a rucksack full of rule books around.
However, I've only had my iLiad six months, there's no way I can afford one of these...
The iRex blog said the the big announcement today would be about software as well as hardware. Haven't seen any sign of the software announcement yet.