A couple of weeks ago I introduced myself in the "Introduce yourself" thread. At that time I had just ordered a PRS-505. It took forever for it to be shipped to me, but I finally received it last Friday.
I can honestly say this device has exceeded all my expectations. The e-ink screen is truly wonderful. I can measure the total success of the device by one simple fact. I keep finding myself reaching to the top right corner and trying to turn the page.
In fact, using it to read has been such a joy, that I have breezed through re-reading Ringo's entire early Posleen series and half way through Ringo and Weber's Empire of Man series (what perfect timing for a vacation).
The only complaint I have is that I am terrified of breaking the screen. Well I also wish the buttons on the right hand side stood out a little more. Other than that, I find this to be a perfect (for me) device.