It is one of my favourites too.
But compared to Powerslave and Seventh Son, lot more people like those albums than Piece of Mind unfortunately, (Songs that hurt Piece of mind unfortunately is the too chessy quest for fire and To Tame A Land which isn't that great of an epic compared to other written by Steve Harris) least from many of the posts have seen on different boards, another one that also gets a lot of praise forgot to mention was Somewhere in Time, another stellar album.