Short version: Yes and No.

Yes.
• If you want to view encrypted programming.
• If you want to view local programs, but your TV device does not have a QAM tuner.
• If you want access to Verizon's on-screen program guide, VOD, Widgets, or access to the Home Media DVR (HM-DVR).

No.
• If you only want to view programs that are not encrypted and your TV device has a QAM tuner.
• If you have a CableCard ready TV, DVR (e.g. Tivo), PC Tuner, etc. You will need to rent a CableCard for each device.

More details follow.

FiOS-TV broadcasts an all digital (no analog) channel lineup that includes local stations, PEG channels, SD (Standard-Definition) and HD (High-Definition) programming, premium sports and movie packages, and music channels. The channel lineup has been changing as more programming is added. Click here for the latest published channel line-ups. Once there, you can view channels available in each plan including Essentials Plan, Extreme HD Plan, La Conexion, HD, Premium, and International.

In addition to the video channels broadcast on the fiber, VOD (Video On Demand) channels are also available. Applets called Widgets can display local weather and traffic conditions, and there is a Program Guide that can display current programming data on-screen.

A STB (Set-Top-Box) is required to view all these channels plus VOD, Widgets and Program Guide on your TV. There are different STB models available depending on desired features: SDTV, HDTV, both with and without DVR (Digital Video Recording). In normal circumstances, a DVR can be programmed remotely, and an extra feature (for an added fee) allows your DVR to play to a TV in a different room, or play some types of media stored on your PC. A DVR can be upgraded remotely by Verizon to a multi-room DVR.

The STB decodes the programming, VOD, Widgets and Program Guide and sends it to your TV. VOD, widgets and guide data are retrieved from the internet via the Verizon supplied router. A more limited video converter (DCT-700) can be used to send SD video to your TV. The DCT-700 does not have VOD, Widget or Program Guide capabilities.

CableCards
A CableCard can be rented from from Verizon for use with CableCard ready TVs or other devices (Tivo, etc). STB Features like VOD, Widgets and Verizon Program Guide are not available on CableCard devices. M-Cards (multi-stream) are available nationwide. S-cards have now been phased-out.

Other popular devices such as a Tivo or Home Theater PC may also use a CableCard to decode video. These typically use a separate internet connection to provide data services like a Program Guide from other sources. It should also be noted that Tivo and several brands of Blu Ray players provide VOD alternatives, such as Netflix and Amazon, however FiOS requires a Verizon-provided device to decode the FiOS VOD.

A television equipped with a QAM tuner is able to receive unencrypted programming without a STB or CableCard. Usually these are the local channels, local HD channels and music channels, also Univision and WGN. Connecting the QAM-tuner TV straight to the coax is sufficient to access the clear channels.