Just a note - if you buff your character with a really high luck the game is more interesting (much better loot and criticals become more common): found ppm9 military in second stage, and a lightened Uzi before reaching the hospital. Shortly after that found a scoped AK-47.
Also give your most powerful automatic to your companion. They've got unlimited ammo, will annihilate the zombies.
I began the game with a luck of 10.
And be careful of accidentally leaving a room when your companion is down! Happens to the best of us...
If tl;dr then high luck = good.