The only TVs that will be affected by this switch are older TVs which receive their signal through an over-the-air antennae. Any TV which is hooked up to a cable box or subscribes to some sort of service such as Comcast , DirecTV or a local provider will transition seamlessly with no action needed from the owner. As long as the TV has a digital tuner, it will still function after the switch. TVs 36" and larger manufactured after July 1, 2005 and TVs 25" and larger manufactured after March 1st, 2006 were required by law to have digital tuners installed.
In order for analog TVs to continue working, a converter box must be installed between the antennae and the TV, converting the new digital over-the-air broadcast into an analog signal which the TV can receive. The government has enacted a $1.5 billion subsidization program to assist consumers with the cost of the converter boxes. By applying online at https://www.dtv2009.gov or calling toll-free 1-888-DTV-2009 consumers can request two $40 coupons per household to be used toward the purchase of converter boxes which cost between $40 and $70.
Small, private companies who target the lower end of the market such as RCA, Magnavox, and Zenith are manufacturing and selling the boxes to their already established market segment. 
High end consumer electronics companies such as Sony (SNE), LG, and Samsung are choosing not to make any converter boxes since the majority of the people who need the products are in the low end of the market, (elderly, low-income, and disabled). 48% of over-the-air viewers have incomes under $30,000, 38% of over-the-air viewers are over the age of 50, and 35% of over-the-air viewers have disabilities.
While several online and phone retailers have been approved by the government for the coupon program, only seven brick and mortar stores have been approved. 
Faced with the option of buying a new converter box to update a dying technology, many consumers may decide to subscribe to cable or satellite services for the first time or expand their current plan to cover all of the TVs in their homes.
In addition to cable providers, many consumers may choose to receive their television from a satellite provider.
Digital television provides many advantages over traditional analog television. Consumers benefit from digital TV's significantly clearer picture quality and better sound quality. Broadcasters such as Time Warner (TWX), Viacom (VIA), and NBC will benefit through digital broadcasting being more efficient than analog. Multicasting will allow broadcasters to transmit multiple free channels simultaneously rather than only a single channel at a time. The government is also benefiting from the DTV switch. In order to offset the government's $1.5 billion investment, it will auction off any unused portion of the spectrum to independent communication companies. The communication companies will use the spectrum for increasing cellular coverage and expanding data networks.