Two applications I know of exhibit a strange behaviour under Notion (as well as under Ion3 and wmii). One is getleft, the other one is Gimp 2.8.x (version 2.6.x works fine). What happens is that windows (not including the main application window) seems to get hidden and redisplayed rapidly so it kind of flickers. If the flickering window is moved to another frame it stops flickering and the problem goes away. In getleft it's not much of a problem, but it makes Gimp very frustrating to use. It can easily be recreated by starting Gimp and have more than one window open (open the preferences window for example).
Strangely enough the problem can be avoided by activating single window mode in Gimp, then hide the docks, and turn single window mode off again. The docks (and other windows) will then be visible still but not rapidly disappear and reappear any longer (and it work fine just like 2.6.x). I reported the problem to the Gimp developers and they thought it could be bugs i the window managers.