I have the countyline PHD on my NH TC26DA, and though I haven't dug a great many holes yet, it has performed well. Very rocky here in the Catskills, but so far I only broke one shear pin when I hit a surprise old bit of concrete in a hole. Busted up the concrete though and finished the hole with no problems.
I have found that you generally have to creep forward a little to keep the auger vertical, but it's not really that complicated, unless you really need absolute precision. Most of my holes have been less than 3 feet so far, and it may be a little trickier if you're trying to get the full four foot depth.
Two very good pieces of info I picked up on TBN before I drilled a hole: 1. Keep rpms low. From what I've seen, minimum is best. and 2. Be very careful not to screw into the ground. There is no reverse on the PTO! In my short experience I had one close call with that, and have quickly learned not to let the thing work for more than a couple seconds at a time without picking it up a little. One guy posted that he has a fencepost that is half post and half of an auger.. The idea of having to unhitch an auger and try to unscrew it out of the ground with a makeshift lever does not appeal to me in the least..