I've had the last 2 generations of the Kindle and love them! I can read the Kindle all day with no strain on my eyes and Amazon's book selection is amazing.
I managed to break the screen on my most recent Kindle (which was my fault) and Amazon overnighted me a new one no questions asked. Couldn't ask for better support from Amazon.
I've played with the Nook and it's not bad, but the Kindle is definitely the best e-book reader with the best book store in my opinion.