It's really not that bad. I did Hard in like, 6 hours. I got everything but the other two difficulty achievements and 'The Collector'. I'm almost done with my Medium play-through and it's taken me about 4 hours so far, with probably another hour to go. On Easy it should be significantly easier. I've just been putting music on and playing through, pausing on cut-scenes to browse forums, etc. It's not that bad if you just dedicate yourself for a day.
Check out my music -- soundcloud.com/acclaimed