Ifyou haven't done it already I'd strongly advise doing the Zombie genocider achievement as early as possible if you have a spare 4-6 hours (plenty of videos on youtube to show you the best routes). Yes it gets tedious but the reward makes achievement hunting SO much easier and you will level up easily 15-20 times while doing it.
Replay value is huge if only for achievement hunting.I'd go with the general feeling of an 8 to 9 out of 10 only let down by some of the retarded survivor AI.Trust me after working through the Saint achievement yesterday and nailing it everytime I now see AARON SWOOP IS DEAD
on my screen I feel like cheering
Sure as hell isn't a breeze to 100% it but there are very few games that balance work needed with satisfaction and just balls to the wall fun like DR does
oh just a note if you didn't know already everytime you do an achievement be it zombie genocider,saint or whatever be sure to get an ending and not just quit and restart otherwise you won't get the unlockable for that achievement unless you do it again with an ending (as I found out to my cost)