oh this is a sore spot.
I come from Cool Edit on PC and have tried pretty much everything in the lower price bracket on the Mac, including Wave Editor, DSP Quattro, Sound Studio, Peak LE/Express and others.
For being straightforward my heart is with Sound Studio. It's a terrible hack of an app by Freeverse who have virtually dropped support for it (, focused on the iPhone, and were recently acquired by ngmoco, a large game developer). Still, I haven't found anything on the Mac that allows me to chop sounds quicker than SS. Yet it's full of bugs, and lacks basic features such as (wait for it).. meters.
EDIT: I just tried Amadeus Pro and it feels promising, and with some getting-used-to it could be my editor of choice. It has all the necessary basics, some odd shortcuts, and some interface inconsistencies (sonogram view). The meters are buried in the Transport window, which is not visible by default (don't ask me..) But at this cost these are no troubling features.
Wave Editor is strong and keeps getting better, but for me it lacks the immediacy of Sound Studio (which has the immediacy of Cool Edit). The multiple window interface makes it feel scattered. If you come from Sound Forge on the PC then it will probably make more sense. I like its extensive support of markers, and niche functions (m/s decoding etc), but it still lacks on the ergonomic front (shortcut keys, quick access to functions). I don't think the idea of Layers translates too well and for me the interface feels sluggish. And then there's the trouble with fades (single click on SS, 3 levels deep menu on WE). For all the nice features, WE feels inconsistent and convoluted.
DSP Quattro puzzled me with the strange choice of just 4 plugins per track. I heartily recommend to the makers to drop the idea and limit the legacy to just its name.
The one software I could never get into was Soundtrack Pro.
There's also Wavepad but I feel an inexplicable discomfort with it. Same with TwistedWave.
I really wish Adobe would port Audition to OSX, and there is a fair chance of them actually doing so, seeing how SoundBooth has progressed so far, and the recent changes to the interface across CS4. Unfortunately CS5 did not bring much news re sound to the table. No mention of Audition 4 either.
There's also talk of WaveLab coming to the Mac, which might sweep the market if Steinberg can better Bias on price. edit: Here it is - version 7.
All in all, it feels like no (Mac) developer actually did research on what we use these things for. And even then I can imagine companies not feeling very motivated with desktop software at the moment, given the portable app market goldmine. The one title that could make some change, without coming from an iphone-obsessed vendor, is Audacity, but that team have no idea what they're doing (pardon the bluntness).
Another problem is that it takes more than just a few launches to evaluate a product and it takes many months to get an idea of how committed a company is to developing their product. In my case with SoundStudio I feel bad but also I still haven't found anything snappier.
Hope this helps.
p.s. I'd love if someone who's tried the higher end (soundblade, peak pro, etc) chimed in with their comments.