I've played through the game 4 times, survival was over 20 hours, nightmare 24, Akumu about the same. I did a newgame+ run of about 13 hours, so I guess around the 80 hour mark in total. I enjoyed the first playthrough the most, and Akumu as I hadn't touched the game since November and only recently finished it.
I want to get all the trophies but can't bring myself to bother with the speed run. I hate stuff like that.