Kindles are definitely worth it. I thought I wouldn't like them but I got one for my Birthday and now I would read it in preference to any Hardback and almost all Paperbacks (although it is nice to feel a real book sometimes).
Also, as it only takes less than 60 seconds to download a book, if you suddenly realise you need something to read on a train/plane journey, you can have it downloaded in the time it takes to put on a coat and get out the door.
Personally I love owning the actual books, keeping them pristine etc (similar for games, I vastly prefer CD + box over digital download) - so for me the kindle isn't as appealing. I just listen to audiobooks or podcasts when on the go.
However dad has one, and I've been re-reading the Hunger Games on it whilst living with him on placement, and it's pretty handy. Comfortable too, since you can read it one-handed, which lets you lounge around on the sofa a bit more comfortably.
I've more than got my money's worth out of my kindle. There are lots of books unavailable on it that I'll need for university (mainly legal guides or textbooks), but otherwise the number of ebooks available is astronomical.
I don't think you appreciate how much easier they are to read until you've got one. You can sit or lie in pretty much any position, and you still just need one hand to hold it and turn the pages. It's lighter than most paperbacks, which makes it easier to handle, and the amount of weight it saves you when you're travelling is significant.
I find there's much less glare on the screen than you get from a book too; not so important on most days in England I guess, but when the sun's out you definitely notice it.
Within a decade bookshelves will have been replaced with virtual projections of the sleeves of the books on your hard disk, so I find even the sentimental reasons for not picking one up to be pretty lacking.
I just ordered the Kindle Touch for £109 (absolute con - so much cheaper in the states. **** you Amazon).
A lot of the books I want/need for Uni aren't on there, but that's not so bad I guess. I'll get a **** load of use out of it over the summer, and a lot of things that I want to read (like Mill's On Liberty are completely free - although I actually have the book...)
What got me is that I can annotate and leave notes on it anyway, which will be good to go back to and add ideas.
I prefer books, I actually have hundreds and I buy 5 or 6 every month, but sometimes lugging them around is a pain and when I go to work I can't take them with me.