In my opinion, the Logitech G9x is one of the greatest mice ever made. Successors to this model were geared towards Massively Multiplayer Online (MMO) games, with large arrays of buttons placed on the mouse and designed to be accessible by thumb for the purpose of calling up any number of customized macro commands. For me, those features get in the way, and the simplicity of the G9x shines.
Using the Logitech Gaming Software, I have customized the two thumb buttons on my G9x; one, to close windows and tabs (Cmd + W) and two, to enter Apple’s Mission Control (F3). For the longest time, these macro commands worked flawlessly. Then with the release of Apple OS X Mavericks (10.9), my Mission Control button would not work reliably.
Pressing the Mission Control button on the mouse would result in an ever so slight hesitation for the OS to enter Mission Control mode. The windows would start to spread out for me to view, but only to then exit back to where I had been. You can simulate the effect by pressing the F3 button on your Apple keyboard and then quickly press Esc. The F3 key will start to invoke Mission Control, and Esc will cancel that command.
Upon investigating, I discovered that if I held the mouse perfectly still, my Mission Control button worked fine; the mouse movement was acting as the Esc key and canceling my Mission Control command.
After hours of work, I found a resolution:
Do not use the “Automatic Game Detection” mode. Use the “On-Board Memory” mode.
The Logitech Gaming Software supports these two basic modes of storing your customized mouse settings. “Automatic Game Detection” presumably stores the mouse profiles on your computer, while “On-Board Memory” stores your customized mouse settings on the memory inside of the mouse.
Once I switched to “On-Board Memory” mode in the Logitech Gaming Software, the problems with Mission Control disappeared.
Just another strange issue I was unable to find assistance for online. Writing this up to hopefully help others having this issue.