[Jmirko]

A question to those recommending the Ipad for annotating pdf-s: can you please explain how this can be done, without the wacom digitiser component to recognise a fine-tip styus, and without the hand-rejection function that prevents unwanted marks on the screen while you are writing on it?
Several colleagues of mine experimented with various apps on their Ipads, but in the end all of them gave up because the writing was slow and unnatural.

When it comes to LCD tablets, my vote goes for the Samsung Galaxy Note 10.1 (Android). Some of the Windows 8 tablets also have true support for handwriting. Older devices (such as the 1st-gen Lenovo Thinkpad Tablet) may be a budget option. "Wacom" and "N-Trig" are the keywords to look for.

E-ink readers are less versatile and usually slower, but they are widely accepted to be less tiring for the eyes, as well as having longer battery life. In this category I would recommend to have a look at the Onyx Boox M92 (alias Icarus Excel) and the Pocketbook 903 and 912. The Irex DR1000 could also be a good choice, but it's out of production and very hard to find.