It's a great rental. Don't bother with buying it, though, you can finish it in four days or so.
For anyone who's unfamiliar with Freedom Fighters, it's a tactical squad stealth/action game which operates under the alterverse premise that the Russians dropped the A-bomb on Berlin to end World War II, and that all of Europe was eventually integrated into the Communist Bloc. With this newfound power, the Bloc starts sending 'advisors' to South American countries and converting them to Communism. As a result, the Cold War never ends, and the game begins with Soviet subs and choppers arriving at the Statue of Liberty.
You're a lowly plumber who, by freak coincidence, is in the apartment of the leader of the main anti-Soviet group to fix a broken pipe when the Russians storm into the city and start killing everyone. Soon, the entire country is under Soviet control, and you're running a resistance trying to liberate NYC.
I think the closest comparison you could get would be a Syphon Filter/SOCOM fusion. You go around liberating key areas and rescuing innocents to gain charisma, which you use to recruit more and more fighters. These fighters join your squad, and you can command them to follow, defend, or attack with the push of a face button. It's really intuitive and easy to learn.