Hi there!
I work with the Electric Hoof Knife and wanted to stop by to answer all the questions posted in this thread so far!
We actually used to use the Proxxon grinder but we've now designed our own one (info on updates can be
found here. The Proxxon grinder is NOT designed to trim hooves (and neither are angle grinders or the air powered grinder I saw someone post about). They are not created of substantial enough parts to withstand the pressures of trimming, and therefore break or don't do a great job. We created our own grinder to use as the Electric Hoof Knife because the Proxxon one actually kept breaking and we had to keep repairing them. That's why it doesn't have great reviews on Amazon - because it's not as well made or as high quality as the Electric Hoof Knife.
Our tool is expensive, yes, but it is made of the highest quality parts and is designed/assembled in Tallahasee, FL for quality control. Our abrasive goat disc is made from durable tungsten carbide that can put a smooth and even finish on a goat hoof in about a minute. It doesn't wear out as quickly as the other tools out there that people have appropriated for trimming, either.
We have people who have three goats and people who have 100 goats using this tool. It is much easier on the hands and wrists than hand trimmers (especially for those with arthritis or carpal tunnel). It also promotes better hoof health because it doesn't leave cracks and jagged areas for dirt and muck to get stuck in and cause an infection. Plus, it's very unlikely you will need a clotting agent when trimming with the Electric Hoof Knife because the disc buffs instead of cuts - you can stop trimming long before the hoof gets pink or raw.
The Electric Hoof Knife weighs only 1.2 pounds and is only 11.5 inches long, so it's not nearly as heavy or hard to control as the big 4.5" angle grinders. A lot of our female customers say they can't handle the big grinders or are scared they will hurt their animals, so they much prefer the Electric Hoof Knife. Someone asked how many RPMs it rotates at - it rotates at 13,000 RPMs which is what we've discovered to be the best speed for hoof trimming.
Most goats (and all animals the Electric Hoof Knife can be used on) don't mind it at all - it's less painful for them than hand tools and they get used to the noise very quickly. We also include instructions on how to acclimate your animal for best results.
We have positive reviews of our tool in Shepherd's Magazine, Goat Keeper Magazine, and on the University of Maryland Wild & Woolly newsletter. We rarely get a tool sent back to us because once people have it they never go back to hand tools.
Please let me know if you have absolutely any other questions! We know it seems shocking to use a power tool to trim, but it honestly makes the job so much easier. This price is high, but our customers always find the benefits much outweigh the cost. The Electric Hoof Knife also has discs for cows and miniature, standard, and draft horses as well, so if you have more than one kind of animal you can trim them all with the same tool.
I hope this has helped clear up your questions!