I've had the Kindle 2 since Christmas and absolutely love it. Played around with the Nook at a B&N, and it wasn't even close. The color screen at the bottom is nothing more than a gimmick. The reader software and other features are much better on the Kindle.
First of all, I'm not going to go into the details about why the Kindle is superior as a BOOK READER to the Android App/iPad/whatever. The Kindle does one thing much better than the multimedia devices, and that's to allow you to read books.
There are several things that I really like:
The way the dictionary integrates with the reader
The way you can search through the book
If you can't find it in the dictionary, expand the search to include Google or Wikipedia
The many free (and very good) books available periodically on Amazon. I've downloaded on the order of 50 books or more that were free and most of them were very good reads.
I ordered a Kindle 3 (WiFi only) for my son, as a matter of fact. I don't really need 3G on mine - I'd be more than happy with WiFi only. I have never come close to being out of reading material and needing a book RIGHT NOW in the boonies without WiFi.