Mine did, he used to look at it, but when left at night he kicked hell out of it! I think he got possessive at feeding time and thought the horse in the mirror would steal his food!
I hope you ordered one with holes already drilled in it. Does it come with a backboard? As if not you need to buy one as you cant fix them direct onto the wall.
Mine is acrylic and it works brilliantly, archie loves it. I often catch him standing talking to his 'friend' when i get to the yard in the morning/evening.
It needs to be mounted on the wall (on the board) from the shoulder height of your horse upwards, so he can see enough of himself in the mirror. Make sure you dont ever feed him near it, as obviously this could cause him to kick out at it.
Totally agree, my horse was on box rest and a nightmare until he got his mirror friend. It was a miracle and he still talks to it. We put ours on a completely flat wall quite high [ this is important] over the opposite side to where he eats