I was very lucky to receive a Sony Reader Touch Edition from my daughter for Christmas. Of the ones currently on the market, it is possibly the best. They all have the "feature" that changing page does take a finite amount of time - a function of the techhnology. I ditched their proprietary software for the PC and loaded a freeware program called Calibre, available here
http://calibre-ebook.com/. Now I can read better (I previously had macular degeneration of the eyes) I am an avid reader, catching up on things. You still have to pay for books that are in copyright, but there are many free downloads of books that are out of copyright and launched on a free commons licence. I also find it very useful for newspapers and e-magazines such as e-Week. To use, it is very simple.
At the end of the day, you need to ask yourself what you will use it for and where. None of them are backlit and so must be used in good light. Also, they have a 6 inch screen - good enough for reading on the train/bus/plane, but bigger would be better for elsewhere.
Sony accessories are VERY expensive - ie, the (optional) mains power supply is priced at £29.25 (Genuine Sony), whereas an eBay sourced PSP power supply does the same job at £5.49, delivered from Hong Kong! Normally the Reader will charge from your PC USB port whilst connected but NOT from a USB-style mains charger!
Would I buy one for myself if I hadn't been given one? Possibly not, but there doesn't seem to be anything better on the horizon for quite some time as far as I can see.
Colin
Update - for a US review - see
http://www.pcworld.com/reviews/product/301948/review/reader_touch_edition_prs600.html?tk=nl_pvx_h_prodrv