I bought my Kindle primarily because I travel a lot and carrying heavy books all the time while travelling has got tedious. I find it REALLY useful as it's light and slim so it can fit into any bag that I have with me, so I can always have reading material just in case I get a spare moment. The battery life is fantastic, I think I've only charged it about 4 times since I got it as it last for over a month (unless you are intending to use it a lot online, which is doubtful as the testing page for the internet isn't that good).
The download function for books straight from the amazon store to online is really fast and reliable, I've never had any problems transferring books. It is also good to have the option to transfer books from the computer to the Kindle as at times I have not had wifi!
The pdf reader function is incredibly useful as currently I am a student and therefore it means I can transfer my lecture notes and/or academic journals onto it and read that wherever I am meaning I don't have to cart my laptop everywhere or find a computer!
The use of the machine is really intuitive, all the menus are easy to find and navigate
However, there are a couple of minor problems. I haven;t found a way of displaying the time on the main screen, this means that it seems a bit pointless having it as a feature on there at all, I may as well just check my phone for the time! Also the zoom function is a bit jerky, and doesn't allow you to see everything anyway as sometimes the image/words go blurry with zoom (however, for the most part this is not a problem as most books don't have pictures).