Whether graphics look bright or dark to people depends on how they have they systems set up. That's why there is an Internet standard for the sRGB color space, so that what you see on your monitor matches what someone else sees on his monitor and that matches correctly calibrated printers, etc.
What matters in the end is brightness and total display gamma -- which is what you see with your eyes on your screen. Display gamma is not the same thing as "gamma" as listed by your video card or in AH -- those are gamma adjustments that sit on top of what all the other gammas in your system are.
There are utilities out there that can allow you to tell what your display gamma is and web pages that can allow you to estimate it and to tell you how to correctly adjust everything to match the standard (such as this one:
http://www.normankoren.com/makingfineprints1A.html ). The Internet standard for the Internet sRGB color space is to have color temperature of 6500, a display gamma of 2.2, and a brightness set correctly.
My display is set according to that. However, my display is a CRT. I've noticed that LCD's often have display gammas way off from 2.2 (like my LCD display at work, which is a higher-end one but which is way off from 2.2).
My guess is that anyone having a system that is calibrated to display gamma of 2.2 is going to see the AH world as very, very dark and that people who have display gammas different from 2.2 (such as with some LCD's) or who have their gamma adjust set to higher than 1.0 all the time may not see the AH world as very, very dark.
Why not just crank up your gamma adjust in AH or graphics card then, you ask? Because cranking up your gamma adjust causes images to look more and more washed out the higher you crank up your gamma adjust. It's much better to have your gamma adjust at 1.0, which is where you should be seeing the images as the designer of the images intended -- if the designer and you both have the same total display gamma -- which is why there is a standard for the Internet sRGB color space.