Update: I got my hands on one.
My not-so-local Barnes & Noble store got their demo unit in today and I made a special trip up to Manassas this evening in order to see it. I wasn't allowed to take photos, but I did spend about 10 minutes looking at it from various angles including inside a darkened cabinet.
This is not an ereader that I would want to use
buy, but I can see the value. I'm fine with tablets, and even if I weren't I have a couple different lamps sitting around my bed (that's about the only place I read in the dark.)
Now, the Nook Glow has a front light, not the back light you'd expect on an LCD screen. That means the light is emitted from a layer that lies on top of the E-ink screen and not the screen itself. With past front light technologies this has led to splotchy lighting, fuzzy screens, and other issues. That's just what you had to put up with.
But that's not the case with the Nook Glow. The light layer was remarkably thin and I had trouble seeing it when it was not on. I've heard B&N insiders describe it as the equivalent of a glare protector and I do think it is that thin.
At its brightest I think the Nook Glow would be easy to read on, and I can see how this might be a useful option for irregular lighting conditions.
Also, the unit I saw was not nearly as bright as B&N's commercial, and that's a good thing. In the commercial B&N faked up a unit that looked like it gave off as much light as an LCD screen. You know, bright enough that you could use it as a flashlight. That is actually far more light than you need to read, which is why I usually read with my tablet's back light turned most of the way down.
The light was relatively evenly spread across the screen. From what I could tell it was emitted from 6 or 7 sources on the upper edge. Counting the sources was difficult at anything but an extreme reading angle (good), so I don't think you'll notice them while you read.
One detail that I found interesting was that the light was softer than on my Kyobo Mirasol eReader. That ereader also has a front light bit it uses a completely different tech for the screen and the light. Its light was evenly emitted from all edges of the screen, so you'd think it would be better. No. The layer used for the screen is much more noticeable as sitting on top of the screen. In short, B&N's tech was better.
P.S. Before you take my opinion as gospel please remember that the true opinion of this device will come from users those first few evenings when they try to read in the dark. I don't think they'll have an issue, but I'm looking forward to finding out what they say. There's a big difference between real use and using a device in a show room.