I use and love total spaces, I also have duet display to use my iPad mini as a second monitor. Only problem is when I activate the overview grid, the windows that are drawn on the ipad display are "whited" out.
Let me know if you can find a fix for this!!!
I'm sure it may affect newer duet displays as well.
I am using a 13-in MBP Early 2011 - with an iPad mini and the duet display software.