If you're a pc person and you're on the fence because of price you might like to know it's like 17 bucks on Green Man at the moment. I still can't bring myself to buy it because these Arkham games seem to have inevitable game of the year editions.
Combat-wise it plays exactly like 3, except you never get into big awesome fights with 10 dudes where you actually get a chance to use your different weapons. Also worth noting that if you just run away the guards almost never keep up with you anyway.
Aveline was awesome, but the vita version of Liberation was a much worse game than 3. That said, I'm probably gonna buy the HD version of Liberation anyway because AVELINE IS SO FUCKING COOL!
After some attempts to connect online and getting booted back mode, my latest story mission disappeared from the map and there was no way to progress; except by going back to an old quick save from hours ago. Watch out for that I guess?