I love Audacity. I've been using this application for years, all the way back into OS9, and it has become sort of my Swiss Army knife of audio editing.
Sometimes, okay, it's a little flaky. Sometimes it might crash, though such crashes are exceedingly rare in my experience. And there may be commercial programs that do the same kind of thing better, though for some amount of money.
But, c'mon... it's free! And it's still actively supported! Aaaand it's cross-platform! When my Windows using friends ask what a good audio editor is, I can point them towards Audacity, and can be fairly certain that they're getting the same experience that I do. So far, nobody has accused me of steering them wrong.
Either way... very useful, well made app, and well worth the download.