I use it all the time. It's a fast, effective, minimalistic tool that does what it does really well. But... I still have to audio copy to use it. It mutes all audio, won't play (even the tempo light goes out) and changes to what looks like forced iPhone 5 resolution when plugged into the effects slot in Audiobus. I'll give it 5 stars, but this needs a few stitches first.
But I still recommend it. Holds sound quality like a champ and it's useful for audio copying or mic recording straight through itself without Audiobus. Also really fun to slaughter songs in your phone's music library with it. Buy it for the fun if you enjoy playing with sound at all, keep it for the AB patches down the road if you're a mobile musician.
I'm running iOS 6.1.3 on a 4S.
And waiting on a Glitch1 update to finish my favorite song. ;)