[soulfuldog]

I don't know specifically if the Glowlight is darker than the ST, but there is a very good chance it is. The additional light guide layer on the lighted screens does have an impact on the screen. It is true of all lighted ereaders. If it has a capacitive touch screen and not the older style infra red touch screen that adds another layers.

In the case of Kobo, there is an argument that their latest reader the Kobo Aura, is in some ways a step back from the Kobo Glo because with the light off the screen is darker/more grey on the Aura (capacitive) than on the Glo (infra red).

For Kindle's some people prefer the basic non-touch screen Kindle ($69) over the Paperwhite, because with the light off (or at its lowest) on the PW, the screen isn't as light as on the basic Kindle. The newest Paperwhite has an improved e-ink screen (carta while everything else still uses pearl) and it has made it a little better.

As Bookworm_Girl says, the answer is generally to get used to having the light on all the time, just have it at a high enough level that it makes the screen pleasantly light, but that you can't really see the light is on. That is why you have the light at a low level in dark/gloomy settings, but if you are in a brightly lit room, you'll possibly have the light at a higher setting. It seems to be the opposite from what you'd think, but that's just how you get the best use of the light on them. And if you use it that way, the screen will look better than on the ST.

However, if you can't get a setting that you are happy with and feel your eyes don't like the light, maybe a lighted reader isn't for you? That is what Sony seem to be banking on with their decision not to use integrated lighting, and there is clearly still a market for that basic Kindle too. Perhaps Nook should also have considered an updated version of the standard ST?