Just curious, but is the reason you guys aren't completely sold on the iPad as a writing device because of the hardware or the software limitations. Hardware can be solved by a BT keyboard. Software will come over time.
The software is excellent - but the hardware is what is lacking (and something that cannot really be fixed)
A laptop has a bigger screen (which is particularly useful if you want to ZOOM into your documents and make the text bigger) and a MOUSE, which will prevent "gorilla arm"
If you really want a portable writing station, I would grab a MacBook Air - the iPad is awesome, but the touch screen affords itself better for graphic design and outlining - a writers dream though is a good, portable laptop