Got it today and must say I can't fault it, yes eBooks are overpriced but I guess you are paying for the content not the actual book. I can get most if not all the books I want on an eBook and I had a 8GB SD card lying about that works perfectly with it which means lots and lots of books.
It's light, slim and looks good. The screen is crystal clear and reading on it is far better than an actual book.
It's easy to navigate books and even the Sony software (which is Windows only) works fine. I'm a bit dubious about DRM on Adobe PDF's which needs you to download another application to verify content.
Soon eBooks will come down dramatically in price and these devices will become mainstream just like iPods.