I went to B&N today specifically to get the XtraFlex2 since I knew they had them in stock. I took another look at the Nook as I was still considering returning the 900 due to the glare and contrast. The Nook definitely has a more viewable screen and the WiFi is nice since I'll usually have access to it.
I got home and tried the light and it does make a huge difference. I really love everything else about the 900 and think I'll learn to work with the screen. In my bedroom I have enough light that it's not an issue but my living room is mostly indirect, low lighting so the xtraflex2 will come in handy there.