Normally, I am afraid of the mirrored wall. It was one of the first things I changed in my last home and before those mirrors came down I can't tell you how many times my own reflection startled me. But, I will admit that the corner mirrors did make the livingroom seem a little bit larger.
Mirrors are now being used in more attractive ways that don't necessarily smack of the 70's. The benefits of including mirrors are actually several.
A mirrored wall will give you an illusion of additional space which is really helpful if you live in a dorm or a small apartment or have a room at home that's a bit too small.
Mirrors also improve lighting situations by giving existing light more reflective surfaces to bounce off of. If you can take advantage of natural light with your mirrors, artificial light can be a bit overwhelming, but natural light creates a cheery glow.
Mirrors also give the room more energy. They capture movement and bounce it back into the room, almost always giving a sense of movement or excitement.
Mirrors are not to be taken lightly, as they can reflect poorly upon your home as well. They are also very heavy and getting the right fit with proper safety considerations should be done by a professional. All aspects of incorporating a mirrored wall into your home should be considered before you take the leap.