We  have these old brick fireplaces, but they are closed off.  This is so easy to install, fairly priced & completely fakes people out all the time!  It really completes the look, instead of having just an empty space there & lends a "sense" of warmth & comfort to the room, masking it feel cozy.  The glow is much more subtle than what is pictured.

Pros: Totally fools people when they glance at our fireplace!
Cons: There is no built in heater if your room needs that extra source of warmth