Best Buy has the PRS-600 in store, and you should have a look at it before deciding, if you can. The referenced thread is taking photos of the PRS-505, which, in my opinion, looks WAY better than the PRS-600. The PRS-600 has a much darker display with much poorer contrast due to the touch screen.
Also, from my experiments with the Sony Touch Edition, the touch is a lie. I could not successfully turn pages with finger touch. It was an incredibly poor user experience. The UI also seemed super laggy to me.
B&N should have a display unit in before the pre-orders start shipping. If I were you I'd take a look at both before you decide.
As for me...I want the iRex. I am not really worried about the stylus. From the videos, it looked like all the navigation done by the stylus you could also do with the flip bar and thumb button.