This is something I often hear at camera club meetings and classes. Even after calibrating a monitor with a hardware device, people are saying that their prints match color pretty well, but they're still too dark.
My response has been that they have their monitor set to bright. But I didn't have a good suggestion of how to set the brightness. Until today. I ran across an article by Eric Chan, one of the Adobe Camera Raw engineers, that talks about monitor brightness. Check you read it on his website, where he gives a tip on how to use your camera meter to help set the brightness if your calibration system doesn't let you set a specific target luminance setting.