Just some comments since I can't review it, given that it requires 10.6.
From what I recall the previous version worked fine on my Mac running 10.5.x, but I never bought the application. Sound quality was really good even at extreme settings, it was easy to use, and had some useful effects (e.g., EQ., Voice Reduction, Mono).
Version 2 adds more features like spectrogram and TAB, but I can't comment on those.
When I tried Capo it was a $40 application, on sale for $20 here at Mupromo as I recall. I have to admit that $20 was a nice deal. That being said, there are plenty of alternatives these days, from the already established Transcribe! and Amazing Slow Downer to other applications that do MUCH MORE than slow down audio, such as Mac audio editors like Twisted Wave, Wave Editor, and DSP Quattro (currently on sale).
Many Digital Audio Workstations also include speed/pitch capabilities. Reaper for example has a very good algorithm, and the current price is $40 for versions 3 and 4, or $60 for versions 4 and 5 once version 4 is out.
To me Capo is a very nice sounding, easy to use application. However, it does not add as much value as other applications that have plenty of useful features, from full DAWs to batch processing audio to VST/AU hosting. With just a bit of work and Jack OS X, for example, I can also use DSP Quattro as a sound enhancer similar to Hear, DPS, AstoundSound, iWOW, etc. I haven't tried it system wide, though.
So for my needs $50 is just too much for Capo. I may take another look by version 3 since I do like it.