I have been trimming for 30 years. Professionally trained at the Michigan School of Horseshoeing. After just a few years I chose to specialize in barefoot care exclusively. Horse's are able to support themselves (and us) on relatively tiny feet proportionally because the foot is meant to move! The frog, the softer connective tissue, acts like a shock absorber. It is the expansion and contraction of a bare foot that keeps the blood moving and the foot healthy. Nailing on a plate of steel or aluminum compromises this natural function. There is definitely a place for shoes in the horse world but there are many more natural options that will benefit both horse and rider in the long run.
Frequent hoof care is really the best and I will teach anyone interested in the basics of trimming your own horses. A knife and a good file and about 10 minutes per horse per month is all you really need.