I got this digger from kellyco and thought it wasn't any good, as I liked what I was using. One day I tried this over at a school yard and I have never used anything since. It is strong enough to push right in, when you move it up and down to cut, it automatically goes in a circle due to it's shape. You can pry things to your hearts content.
I prefer the Kellyco Gator Razor Edge digger myself. It is narrower than the sawtooth digger and serrated on both sides, but does need to be sharpened when new. Being narrower it is easier to make smaller diameter holes which is in my opinion a paramount consideration in not messing up lawns, parks, schoolyards, etc. Many here use the Lesche digger but I like the Gator Razor Edge a whole lot better. Lifetime warranty and built really strong.