The Mac OS dock is a thing of beauty. It’s look and feel have been recreated on various other devices, even as a tool (Rocketdock) for Windows.
Under OS X Mavericks I recently found a minor frustration with the dock though. It appeared to randomly keep switching which of my two monitors it would call home.
I couldn’t put my finger as to why, nor could I find a way to re-create the problem. It just happened and the only way I found to put it back where I wanted it was to reboot.