I've reached what looks like the end of the game now. The Survival Horror parts gets a lot more frequent during the main quests towards the end of the game. If you don't do all the side quests it probably takes up around half of the total gameplay. BTW, the final boss is one tough nut to crack.
DP is in some ways very similair to Lynchs Twin Peaks (more so then Alan Wake). But it definitely got its own twists (and "seeds", so says Mr. Stewart).
