I like it. It's not exactly the fastest, but its meant to be read and it does well in that area. The contrast is similar to other readers like the kindle or the nook, but those are a bit better. I've never used that sony model and the one I saw today in Best Buy was broke so I can't give you too much of a comparision. It recognizes books within random directories too.
I personally think it's useful for it's main intended purpose: reading.
Web-browsing and other stuff is a nice addition, but the ePaper screen isn't too fast at refreshing color images like LCDs. The Clarity is very nice (pixels aren't seen unless you hold it really close), although it requires at least a close light source like other readers. The part I like the most is that it runs linux, which can be modified very easily.
If you want to see videos, etc look up the 4fff N618. This is the original model. Other companies just create their own firmware