As a decorator I like to use mirrors in a home for different purposes.
A mirror can bring light into a room, open up narrow hallways, it can also give the impression a place is bigger than it is. Ultimately, it can make a statement as a decorating piece adding glam to any home!
It really depends on what you are looking to do with a room in order to choose the right shape, size and design of a mirror.
I personally love mirrors in the dining room area, I think it makes a statement and gives any space a glamorous finish like in the picture below, I got this mirror from Home Sense for the fabulous price of $199.00. (It is hard to see the size in this picture but it is pretty big.)
AGK Design Studio. You can find a mirror similar to this one from Restoration Hardware or worldmarket.com
One Kings Lane.