Forms Mode comes in handy if you want to see how TurboTax filled out a form or schedule, or if you need to dig deeper and find out the source of a calculated figure. Also, if you want to override a calculated amount (which we don't recommend), you must use Forms Mode.
Most of our customers will never need nor use Forms Mode, which is exclusively available in the TurboTax CD/Download software.
That said, for our tax-savvy customers who like to see what's going on "under the hood"— not to mention our support staff — Forms Mode is a very useful and powerful tool indeed.