oh man.. farrier is so important!
One thing I HAVE to have in a farrier is understanding how to balance a hoof properly. Getting the right angles, whether barefoot (how we roll) or with shoes.. they neeeeeed to understand that concept or I will NOT let them near my horse!
Pluses are professionalism (calling if they will be late, NEVER being late, respecting my horse (who I will make sure respects their space.. aka no snuggling, slamming hooves down, kicking, biting, pushing, etc.), reasonable prices (right now it's $45 for a trim) and my horse needs to get along with this person as do I... I've had farriers undermine me, be rude in general because of my age.. and it really irks me and of course my horse too.. and it doesn't end well.
But they are SO important, I'm very lucky to have found a fabulous trimmer the first time around.. and I just moved here!