I have one and I love it. Some books (both pdf and not) are electronically compatible and searching is simplicity itself, others are not and are a bit more cumbersome, but in terms of usability, it is a marvellous thing. I too find screen reading tiring, but never with the kindle. It's not back-lit so there's no glare, and it's just like a page even in direct bright sunlight.
As far as price goes, many books are not as cheap as one would hope, though mostly cheaper than paper versions. Often, though, they are quite cheap, sometimes very cheap, and there is a huge number of free books available.
I love mine!