We've finally got the details on Fiora straight from Riot, and it seems the information that was leaked earlier this week was accurate. Riot is billing this champion as a "melee carry", what I'm guessing is a different iteration of Master Yi or Talon.
Duelist (passive) - Fiora regenerates health over 6 seconds each time she deals damage. Striking champions will cause this effect to stack up to 4 times.
Lunge (Q) - Fiora dashes forward to strike her target, dealing physical damage. Fiora can perform the dash a second time within a couple seconds at no mana cost.
Riposte (W) - Fiora's Attack Damage is increased. When activated, Fiora parries the next basic attack and reflects magic damage back to the attacker. Works against champions, monsters, and large minions.
Burst of Speed (E) - Fiora temporarily gains additional Attack Speed. Each basic attack or Lunge she lands during this time increases her Movement Speed. Killing a champion refreshes the cooldown on Burst of Speed.
Blade Waltz (R) - Fiora dashes around the battlefield to deal physical damage to enemy champions. Successive strikes against the same target deal less damage.
You can read Riot's entire write-up on Fiora here.