TwistedWave is a very easy-to-use and powerful audio editor. It supports Audio Unit plug-ins and many file formats, including wav, aiff, caf, mp3, mp4, FLAC, and Ogg Vorbis. It has good multichannel support, so you can apply Audio Units to a selection of channels. It supports unlimited undo and redo, which work instantly. Zooming in and moving around the waveform is very fast, even with very large files. All the effects are applied in the background, saving a lot of time.