I had a Nook GL reserved and went to pick it up yesterday. Before I went back to the service desk I noticed they had both the ST and the GL on display so I decided to do some comparisons.
I had read all of the reviews and seen peoples comments that the new one has less contrast and thought people were just nitpicking. Seeing it in person though I have to agree it is an issue. One of the things I love about the ST is how crisp and clear the "ink" is, the new Nook has more of a washed out look and the text is sort of gray in comparison to the old Nook's black.
It's probably true that when using the GL by itself you will get used to it and there really isn't a problem reading the text on it. Still it was hard for me to justify spending $90 more dollars for the GL (ST on sale for $55 at Staples this week) for a reader with an inferior screen.
If they can get the GL text to look closer to the ST and add the ability to find text in books by highlighting (the NT has this) I'll be all over it and will likely sell my NT.