I asked the same question here about three months ago.
I bought the Entourage Edge and would sincerely recommend it to anyone who wants a good reader with a large screen for his or her research. It allows you to annotate (freehand), draw, to add notes to your PDF, highlight. You can write notes separatly from a pdf file, since there is an app called Journal. You can add as many notebooks as you wish. There is an option for attaching an external keyboard. You can also do some light Office editing.
The best thing is that when you annotate or highlight a word, the Edge automatically adds a bookmark with the name of the highlighted word/phrase, so that you can find/edit it very easily.
It has tons of very useful apps and gets improved with every firmware update. You can check out the videos on their webpage, just to get an impression of what this little device can do. I hardly mantioned its features, since it's more like a combination of a netbook and a ereader. It can do pretty much everything these two devices can do.
On the other hand, you can freely surf the web, Wikipedia or whatever you like, since it comes with WiFi, browser, mail application etc. I'm typing this on my Edge
. You should have in mind, however, that its weight is about 3 lbs (like a netbook).