Share 'How effective is the Powerball?'

I've been trying to look up some key exercises to help improve my overall fitness and also help with better distance. I know proper form plays a big factor but I'm sure a solid core and some power behind my rips will help too. I already do pull ups.. push ups.. abdominal crunches. I've seen this "Powerball" device around the internet. I was just wondering from some of the owners of this device...…