The free-flow fighting system is one of the best features of the game. The free flow fighting systems allows the player to see finishing moves and certain CG scenes in slow motion, like the "bullet-time" moves in the Matrix films. In a show of good judgment, the game doesn't use the slo-mo for every other battle move. It's used sparingly and mostly for finishing moves.
The one thing that makes the game so great is the atmosphere. Instead of being a straight forward action game, the game looks and sounds like a very scary horror film. The island of Arkham is isolated and dark and the various buildings on Arkham look menacing. Many of the rooms located in the mental facilities look more like torture chambers than places of rehabilitaion.
One last thing I want to mention are some of the character redesigning they did; some which were Killer Croc, Harley, Bane & Scarecrow. Harley was transformed into a slutty looking crazy nurse, which fit the story, Bane's redeisgn looked very lame - they made him look like the joke from the Batman & Robin movie circa 1997 and Croc was made to look more like a monster which was pretty good. Scarecrow's redesign was the best of the bunch. I've always felt that Scarecrow looked okay at best and a joke at worst. In the game his costume was almost completey re-done to make him look more like a threatening sadist; he was given a brown hood, gas mask and a synringe was on top of each finger. My description doesn't do it jusice so some images:


Harley

This one made me laugh

Unfortunately Bane


And Croc

I strongly reccomend this game to even any gamers.