I do not like boots on my horses. Here's why : #1 I don't believe they really do anything for them. #2 If they walk through water at any point in the ride (even if they don't soak up water) and then go through any deep soil or sand, they will tear up the skin under the boots. I've seen several horses cross rivers and mud, then ride for the rest of the afternoon thinking they were ok, only to pull the boots at the end of the ride and have the hair worn off, and very raw legs.
I think if you're using them in a dry arena with a dry horse, you're fine, but on the trail, I think they're a gimmick. Just my personal experiences.
Ask Often, Demand Nothing, and Reward Generously.