I've used my daughter's Kindle and I have the iPad2. I like them both for books, however the iPad's ability to do much more than just be a book reader hooked me. Viewing and creating photo albums on the iPad alone should be a deal breaker, but it's email, music, and just plain "neat" factor as well as the 1000's of apps should make it the choice.
The 10 hour+ battery life is indeed real for the iPad. It is no good for bright sunlight, thought. I use my iPad for books about 60% of the time it's on. When there's WiFi or cell signal available, I hardly ever use the computer for email checks. The iPad is just to easy and fast for this.
BTW, the iPad will allow you to read books in any file type that may be exclusive to other readers, ie, Kindle, etc.