Simialr position to both Adam B and Mycropht. I have a mix of PDF A4 docs, text files and a subscription to Safari books, I also have PDF copies of all my hard copy RPG's and being able to carry them around with me sounds fantastic. The prospect of reading any of these on todays 3" PDA's is not at all interesting.
Aside from the size the battery life issues put me off if I am able to I can read for 10+ hours and having to stop due to low power well

.
Next searching and interactivity is paramount somthing to replace flicking through a 30 page paper to find that paragraph/diagram, thinking about opening a single page at a time makes hardcopy very attractive.
Lastly Price, I have little spare cash and well £400+ for a device (ie iliad) is to much or the £500+ for a laptop which is to bulky and waaay over powerd of £1200+ for a tablet still over powerd if not so bulky. If there are any suggestions for this device I am all ears.
You know a N770 with a slightly larger screen and higher resolutionwould do at around £150