Not that it does anything badly -- the speed and pitch manipulation are very impressive. While there's a little bit of clipping and distortion at the absolute extremes, that's to be expected when you're changing these attributes on the fly, and when you're not at the extremes, things sound really great here. The app is extremely responsive to the controls as well, which are very intuitive and well designed -- you can choose to quickly select various tempos or pitches on a meter, or drag the slider in between those to find exactly the point you want. And no matter how fast you move the slider, the music responds instantly without any noise or slowdown. If you want to change a song's pitch or speed in order to try to play along with it or give it a closer listen, Capo will let you do exactly that, in style.
But at the same time, that's where the functionality stops. Bringing music into the program is not quite as intuitive the rest of the controls -- you can bring in tunes from your iTunes playlist through the "Open" menu, but the first screen just asks you to drag music in rather than giving you the browsing option right away. And if you don't already know the chords or notes to a song, Capo won't help you with that -- it'll help you slow the song down so you can hear them better, but if you can't tell what they are that way, you're still out of luck unless you go find them elsewhere. Maybe it's a lot to ask an app to tell me what chords are playing in my songs, but given that Capo's page says it will help you "learn your music," and calls it "an essential part of a guitarist's tool set," that's something I kind of expected.
There's no way to open a side window to mark tabs or show lyrics -- you can put custom verse, bridge and chorus markers in the song, but those don't appear as much more than flags on the top timeline. It seems like it would have been a good idea, given that you're probably playing with this app open, to let you mark chords or lyrics in the window. In fact, there's no evidence other than the name that this is even supposed to be a music app -- if you just wanted to pitch-shift someone's voice track, you could do it in here, and there wouldn't really be any features going to waste.
And it's for that reason that I consider the app pricey -- at 40 bucks, I was hoping for a little something more than just a pretty pitch- and time-shifter. It would be nice if the app really did commit to help you "learn your music," rather than just slow it down to your speed and transpose it to your key (whatever that is -- the pitch meter goes from -24 to +24, so there again you need to either do it by ear or figure out for yourself how much you need to move the meter to match up). But if that's what you want to do and $40 is what you're willing to pay, Capo is a great app.