Just completed it on Medium. Brilliant game, couldn't put it down.
Now to 100% it and do the challenges. Combat modes seems hard - variation seems to be the key to getting points, I found a list (PS3 version)
Freeflow Perfection: Perform a perfect combo including all of Batman's combat moves (any play mode)
[ ] - Strike
/\ - Counter
O - Cape Stun
X X (double-tap) - Evade
L1 - Combo-Batarang (Related: a skill will make this more powerful, highly recommended)
R2 R2 (double-tap)- Combo-Batclaw
R2 + /\ - Ground Takedown
/\ + O - Special Takedown (Unlocked skill, requires combo of 5x or 8x)
[ ] + X - Throw (Unlocked skill, requires combo of 5x or 8x)
The predator challenges seem easier?