Paranoia.

The enemy sensing radius is FAR beyond what I was used to with my first two characters at default 5 perception.

I'm looking 360 degrees all the time thinking I am being ambushed. LoL

"Oh snap! More viper leaders or Giant Radscorpians? Wait, where are they?"

I have mine naturally low for that purpose xD works well for me though I guess because I am using melee rather than guns.

I have mine really high because I use explosives. I also have ED-E, and it just keeps wandering off and attacking enemies.

Do you use the Grenade Rifle?

If so make sure you get this if you haven't:

http://fallout.wikia.com/wiki/Grenade_Rifle_Long_Barrel

Grenade Rifle is almost unusable without it imo.

Haven't gotten to Novac. I've been exploring around Nipton for 10 hours now >_>