I use it as a way to push through mental pain when I am not running. I once went 7 minutes because I had nothing to do for 7 minutes, so I just wanted to see what I could do(I am not a complete stud, I was doing core before this). I was suprised, but the main things that it helped me with were:
1. Lower back strength. Especially helpful if you are a beginning runner. Believe me.
2. If you focus on your breathing, it could become a breathing exercise, just focus on slowing down your breathing. This actually helps me somehow with slowing down my breathing during a long run and some tempos. Magic.
3. Lastly, it becomes both a way to keep your heart rate down as well as a mental thing. I do it when I am feeling out of shape(I have not run for a week), or when I need to push through mental pain(League Finals coming up), it is not really for my core that much anymore.
-EGF