I don't have perfect vision, so these sort of glows kick in automatically, especially when I'm tired. I't problematic enough to make me switch to a lower contrast theme when I work at night. It would make sense to apply an effect like that only if it were _increasing_ legibility.
Take a look at this a demo pic: http://cl.ly/image/1i0x2X3W3G0x
Notice the rare case where the drop-shadow helps increase the contrast between foreground and background. You'll get props for doing that any time you pull it off.