Honestly, I had a blast with it. It's no Arkham, but if you don't go in expecting a materpiece. You might have more fun with it than the reviews make you think.
The best parts are easily the character interactions, they are all very interesting. All four of the knights have interesting problems that fit their characters extremely well.
The combat is simple, but is at least more than pressing three buttons thanks to the momentum abilities. And the court of Owls was a very interesting enemy faction, their hideouts and area's were easily the highlights.
The boss fights also manage to be very fun, and challenging. The game has it's flaws, but WB Montreal knows how to make a good boss fight

All in all, it's a fun romp that is probably best played with friends (I couldn't tell you, I don't have any). Don't go in expecting Arkham, and you'll probably have a fun time with it