The program does exactly what it claims to do. It allows you to "bookmark" into existing audio files. This could be useful for live recordings of concerts where you'd like to note where a song starts and ends, or particular topics of a recorded meetings.
I was a little bit leery of the "rotate your finger around the dial" interface, but I now admit that it works pretty nicely and has advantages over a simple timeline, especially for long recordings. When you "just miss" the start of a particular section you wish to bookmark, a simple flick of your finger brings you back a few seconds.
This would be more useful to me if it could be use to bookmark videos the same way it does audio files, but as I said in the title: it does what it says, and it does it nicely, hence my rating.
No advertisements (yet!), no distractions, and pretty useful.