I just upgraded from Ubuntu Lucid to Maverick, which took me from exo-utils 0.3.106 to 0.3.107. When using exo-open on a text file, the new Mousepad window is created without focus, though it was created with focus when I used the older version of exo-open. When I use gnome-open instead, Mousepad receives focus as expected.
Fixed in cefcc4f.