I use Audacity. It is open source and gets the job done. The majority of what I record is Vox. Some of the limitations with Audacity are: Audacity lacks dynamic equalizer controls, real time effects and support for scrubbing. MIDI files can only be loaded visually. I also use it as a multi track recorder. Of course I am new to recording on PC and am curious to see what others are using.

I believe that Audacity can be extended using through VST plugins, which greatly expands the capabilities. I have used it in Windows and it is pretty good there. In Linux it is pretty ugly :(

I use OSX, and the audio editor that I use is called Amadeus Pro. It was pretty cheap, and just like most things Mac it is very simple to use, the interface just kind of stays out of your way. You can see the software at http://www.hairersoft.com/AmadeusPro/AmadeusPro.html.

One thing that is annoying with it is that no matter what you have the audio file(s) associated with, the software will associate any files created with itself, so you have to keep going in and manually fixing that with each edited file. Pretty annoying!!!