I have one of those two handled post hole diggers and had a lot of frustration with it so, faced with digging 22 post holes, I thought I'd give this auger a try.
At the time of writing this review I have dug 20 of the 22 holes for my fence and I am overall very happy with the purchase. My soil consist of about 6" of top soil and then pretty heavy clay for at least the next two feet. Digging the holes was hard work but enjoyable and the auger did not struggle with the clay at all. That said, I was only able to dig it down a couple of turns otherwise I struggled to pull the device back out again due to the friction on the sides of the hole. So I would end up screwing it down a few inches, pulling it out, decanting the clay into my wheelbarrow and then repeating.
Rocks, however, are the auger's nemesis. Small stones are no problem as they are pushed between the spirals of the blade and come up with the soil. However larger rocks (like I was lucky to have in about 60% of the holes) simply stop the auger in its tracks. I tried a variety of ways to deal with rocks but eventually resigned to having to prise them out with a crowbar by hand. The rocks in my garden average around 5-9" wide and it was very hard work and time consuming removing them. Unfortunately when you get a large rock under the point of the auger there is no way to make progress and you have to use some other tool (like a long spade or a gardening trowel) to get the soil out so you can see what you're dealing with.
When the path is clear of rocks, however, the auger leaves a very tidy hole which minimises the amount of concrete you have to use and soil you have to dispose of.
The supplied wooden handle's girth is a little narrow for the tube of the auger which means it falls out whenever you lean the auger up against something. I cured this by putting some inner tube rubber around it so it's not that much of a bother.