It is still in beta, but Audacity 1.3.2 is available for download from Sourceforge.net and from an afternoon spent with it on a Windows XP SP2 machine, I can say that I like it better than any other audio editor I have tried (and I have tried many). Plus it is open source and free! Well, I do have one beef with it - it doesn't support DirectX plug-ins.
I upgraded to this version for the simple fact that it now supports saving (exporting, writing, or what ever you might call it) multichannel wav files. All other audio editors these days seem to have been streamlined to support only CDs (i.e. two channel), surround sound (5.1), or similar mass market formats. Of course, if you are messing about with microphone arrays, being able to save multichannel files is more than a convenience. Adobe pulled this feature out of Audition (editor's correction) (formerly Cool Edit), much to my chagrin. Things haven't been easy since.
You do have to configure Audacity properly first, however, as it won't allow it in its default state after installation. To do this, go to Edit/Preferences to pull up the panel for setting the application's preferences. Then select File Formats and tick the radio button labeled Use Advanced Mixing Options. When you get ready to save your multichannel file, simple choose File/Export As/Wav and it will pop up a handy panel to let you select which track gets recorded to which channel. Very nice.
This version also seems to be faster at loading and working with multichannel files. All editors that insist on displaying the time waveform (and that would be just about all of them) go through the entire file at first load. This can take a long time when you are talking about some of my files - 64 channels, 24 bits, and at least 16kHz sample rates.
BTW, you can also select how many channels you wish to record to under the I/O heading in the Preferences Panel. I haven't tried this with an external digitizer yet, but I will do so soon on a MOTU box.
(Notes: "Audacity" is a trademark of Dominic Mazzoni. Audacity is licensed under the Creative Commons Atribution License Version 2.)