^^^Yeah, it does have trophies.
Just finished this tonight playing through it split-screen with my brother. He played through as Night-Owl, I was...er...the other bloke.
The basic gameplay is that you enter an area, are attacked by a handful of dudes and then move onto the next area. Enemies are not as same-y as the reviews indicate: blokes without melee weapons, blokes with melee weapons both usually accompanied by a bigger bloke.
There are areas where the two split up, usually to open up a door for the other character but sometimes going by different routes to the same destination.
The two characters have slightly different attack options and there are little tokens that have to be walked through to open up some moves. Night-Owl has a groovy 'electrical' attack, whereas er...the other bloke has an equally groovy rage attack.
It kept us going for 3 days, though admittedly we weren't playing it all the time. It wasn't brilliant but, it wasn't as bad as I was expecting. I only really bought it because it's 2 player lure and as a co-op experience it was reasonably good fun.
Unless your a die-hard fan of the film/graphic novel or of fight-games, I'd stick with the free trial on PSN for an example of the gameplay.
If your on the look-out for a 2 player offline Co-op, then you'll have a laugh, especially at the sick finishing moves your partner carries out.
Lovely.
ETA:
Played this through solo with both characters and took between 5 and 6 hours. Admittedly it my have been longer if I hadn't played it through with my brother the first time. I died a couple of times with Rorshach but not at all with Night-Owl.
One thing I didn't mention was the story, which whilst nothing amazing, does leave the possibility of something better and involving in any future download...