I am unable to "pinch-to-zoom" on my magic mouse in mountain lion. I am using better touch tool (but have tried disabling that and pinch-to-zoom still doesn't work). In better touch tool under mouse > other gestures (zoom, etc.), it talks about changing sensitivities for normal predefined actions (which I think is what I want) and keyboard shortcuts (not what I want). I have tried setting these higher and lower, but I still can't pinch-to-zoom with my magic mouse (like I can with my trackpad).
If anyone has any suggestions, I would much appreciate it!