I started out with dark backgrounds because of vim + Linux. The default terminal was black. Now I use the dark background w/ color text for all my editors/IDEs. I tried switching to the white background for a week, but it really hurt my eyes. I had to switch back after a few days.
Same experience here. I start having difficulty coding when the background is too bright, or even when the text is too bright on a black background (I had the text be a light gray for nearly a year, and I never really realized it wasn't white. Then when I looked at white on black code, it looked very bright and unpleasant to read.)
Could you elaborate more on your situation? Did you always use a dark background? What are the conditions around where you code?
Light grey on black for me is still too hard to see. I prefer pure black and white. On the Windows Command Prompt, I set the default color to 0F instead of the default.
My concern is not so much with a dark/light scheme, but with color contrast.
Currently, I use Vim with a dark colorscheme ('desert') and I love it. My friend, Aaron, also uses a dark colorscheme.
However, my other friend, Brian C., has an affinity for light backgrounds. Whenever I show him code on any dark colorscheme, his first response is to make it white. Then again, that is his normal setup; that is what he always deals with.