Deffinately one of the most amazing tools ever invented. Once I built the guide (about 7 minutes), it took precisely 47 seconds to cut a damn clean circle out of the top of my new keggle. With setup and cleanup, I did it in my half hour lunchbreak at work, and had time to eat.
Anybody who is converting a sanke should find someone who has one, or somewhere to rent one. You won't regret it.