My one lifelong hobby is reading. My house is full of bookcases and my floors are covered with books that don't fit. I read a lot of non-fiction: history, science, philosophy. I always tell people I haven't read sci-fi since my early 20s, which really means I only read 2 or 3 sci-fi novels a month. Typical geek reading really. One of my biggest challenges with travelling is choosing what books to take. I like to travel light, and I've gone on trips where half the weight of my luggage was books...and of course, none of them taste good on the trip so I have to buy other ones.
In February, I bought a Kindle to take on the airplane, but (much to my surprise) started reading it on the bus and now prefer Kindle books for reading in bed. The weight is perfect. I've loaded my Kindle with classic "Big" books that I can dip into when I want to. For example, Russell's "History of Western Philosophy" at 700 pages; all 3 volumes of Stephenson's "System of the World" trilogy, each about 600 pages; "War and Peace"; the Pepys diary. These are much easier to read on the Kindle.
The battery life is excellent: 1 week if I am reading heavily (vacation), 2-3 weeks when I'm only reading an hour or two a day. Early complaints about battery life seem to have been from people who didn't understand they should turn the wireless off (it's lousy for reading the internet and blogs...Amazon may have been better off not including those features and focusing on books).
Book selection is still an issue...however there were about 90,000 books when I bought the device and there are 165,000 today. On a monthly basis books come out I was looking for earlier. However we still need 10x more books. For example, looking under English history Amazon lists 794 Kindle books versus 98,000 book-books (many out of print and obscure of course).
The device is no beauty. I think a lot of folks are turned off...expecting Apple-grade industrial design. Fine...another Amazon mistake, but if you are a reader, you won't notice the looks after the first 100 pages. The Next and Last page buttons are too easy to hit. The page transitions are slow...this is a fundamental problem with eInk that is going to take time to fix. The pages are slightly too small...you have to switch pages a lot. Forget pictures, let alone color. The Kindle is for reading books--big books like the ones I have on it, not for looking at pictures. All in all, the device needs to be improved, but the weight and the clarity of the text make up for these other deficits.
The real key is the Service. Amazon absolutely nailed this in Version 1. You order a Kindle from Amazon's site and it comes pre-configured for your account. You have to plug it in to start charging the battery, but you can use it while it charges. I use my laptop and the web to buy books...Amazon's site is far easier to navigate from a laptop than from the Kindle itself. You find a book, you One-Click it, and within a few minutes you can start reading it. I've bought books on impulse right before running for the bus. There is no wireless configuration, no settings you need to input, no passwords or authentication. It just works.