Terrible. I bought this app in order to convert one video file to audio in order to save it to Dropbox, as the video was too big.
I downloaded the free version and waited for the file to convert, only to learn I could only save the file to Dropbox with the paid version.
I downloaded the paid version and had to reconvert the file. When I tried to save the audio to dropbox, I was told I had to use the paid version.
Nightmare. Luckily it was only $3.49, but Id strongly recommend against inviting this particular frustration into your life.
That said, I tried the other two video to audio apps I found in my search and found them equally useless.
LilyL. about Video To Audio Pro - To mp3, v1.2.0