Audacity is OK for simple cuts and processing, but for the sort of editing where you are pasting good bits over bad bits, it's either a complete pain or I have missed some essential detail about how to use it.

I use Ardour (mainly a Linux package but there an OSX version too) for fixing mistakes in recordings and multitrack recording, and Audacity for simple jobs on a stereo file.

Reaper is said to be an excellent multitrack editor and mixer for Windows. It's not free like Ardour and Audacity, but is very reasonably priced and you get a fully functional 30 day free trial which then becomes nagware.

Ardour
Audcity and Reaper summary.
Audacity
Reaper