Finally a bright future for MyPaint! (as well as Gimp and Inkscape I believe), a major bugfixes release has landed. See datails here http://ftp.acc.umu.se/pub/gnome/sources/gtk+/2.24/gtk+-2.24.8.news
All (most?) dreaded GUI and behavior issues have been swept :) tablet issues such as pressure and tilt also fixed. Hopefully they will bring GTK+ 3.x to the same level for Windows too.
MyPaint will use GTK+ 2.24.8 for the upcoming and long awaited 1.0 release! yay!