I use sox.
I've seen a handful of your posts about using sox. I gather it offers a command line UI only. (Though it wouldn't surprise me if there are graphic UI front ends available.) I'm curious: how do you handle situations (upon which I come across regularly, some more than others) in which you want to apply time- or selection-specific edits? For example, tracking of a continuous performance or of select portions of a performance, volume envelopes, selective compression / limiting, crossfades, noise reduction based on a selection of noise, etc?
I do most of my edits beyond resampling, concatenation, and stuff in audacity. Hard limiting and other things. I've even gotten around to writing a few nyquist routines for audacity. Or at least modding existing ones. I like libsndfile's resampling routine better than sox's routine. Sox is mainly to get the speed effect going to sync my FH1 and Korg MR-1000. Otherwise outside of some file format conversions I try to avoid sox, as it has flaws. And most of my edits to extract specific segments of audio I do in audacity. But there's some oddity's like porting speex's AGC routines to sox, that keeps sox in play on a lot of things. And libsndfile doesn't seem to have a speed option yet. At least not on the command line. There are gui front ends to sox, but I normally find those limited and/or out of sync with the latest version of sox.
Otherwise most things filter, limiter, compressor, gain, and otherwise I do in audacity. Although sox does have a neat trick for segmenting out a DAO CD at regular intervals.
$ sox LargeAudioFile.wav track_.cdr trim 00:00:00 00:02:00 : newfile : restart
Assuming that LargeAudioFile is 16 bit and 44.1kHz, otherwise you have to explicitly tell sox the input and output parameters. I output CDRs because that's what the CD burning software converts it to anyway, and if you're doing multiple copies, you save a little bit of time on the repeat. Less so as computers get faster and faster. In either case, less cpu usage equals less heat equals lower power bill(air conditioning). Not by much, but every little bit helps.