I've just added a new tutorial to the New Tips and Tutorials by Jinny section at PixelAlley that I think will provide a solution for you and others if you have trouble seeing cursors, selections, etc. when working on a 50% grey Canvas or Layer:
How to See Cursors, Selections, and Transform Controls when Working on a 50% Grey Canvas or Layer, by Jinny Brown (http://www.pixelalley.com/tips_and_tuts/see_cursors_selections_on_50pct_grey.html)
Thanks to a member at Conceptart.org's Painter forum for asking the question and pushing me to think of an easy solution.
Let me know if it works for you as it does for me.