Home Office deduction

Several years ago I decided to leave the office I had been renting and start working from my home.
There were advantages and disadvantages.
On the plus side, I saved the rent, used an office space available in my home and was able to deduct a portion of my mortgage interest, real estate tax, utilities and other home expenses as a business expense. The deduction is based on square feet used; e.g. if you use 400 sq feet of a 4000 sq ft home for an office, 10% of all relevant expenses are deductible. You can also take a deduction for depreciation of 10% of the home cost or other basis (excluding land value). Another big advantage is that I save car expense and I don't have to hang around an office when I'm not busy--I can watch TV unless something comes up.
The main disadvantage is that I don't get as many new clients, since I live in a residential area and I can't hang out a sign.
It's a pretty good trade-off.

To deduct the home office you must use it exclusively as a business office. Having a TV in the office could disqualify it on the grounds that it is not exclusively used for business.