IMO, B&W ebook readers can never fit in my classes. I have many colored diagrams. So I bought an android tablet currently on Froyo (will soon get honeycomb upgrade!
).
The main advantage of using tablet instead of e-reader is, I can read virtually any format of book. Secondly, I couldn't wait for wikipedia to load even for 1-2 seconds and when I am out of range. The wikidroid does all work. Offline wikipedia FTW. Thirdly I can underline and highlight text in different colours, that's crucial for me. ThinkingSpace app is boon for college students. I can make mindmaps in the same easy format as I do with Freemind on my laptop; and both have same format, so I can sync.
Conclusively, I bought the tablet which replaced my e-reader just because of huge number of apps and possibilities of doing everything on my tablet.