After seeing this video
http://www.youtube.com/watch?v=FVj41...eature=related
made by an Asus Eee Note early-adopter, I don't find this device so interesting anymore: it seems like, as usual, not all PDF's display correctly - and I guess technical PDF's are most likely to be part of the bad ones.
It's amazing that among all the (mostly useless?) electronic devices that are released each month, none of them was made for the (apparently simple) purpose of reading PDF's... For instance, the Motorola Xoom would display the full width of a PDF with its 21.7 cm wide screen, but it wasn't designed for annotations.
I'm starting to think that the best solution would be a tablet PC. Lenovo's and Fujitus are out of price (2000+ US$). HP released something more affordable and interesting (HP TM2): a 12'' screen including a wacom matrix, at about 1000$. But this device is thick (about 4 cm at the thickest) and massive (more than 2 kg), not practical to have it on the go