My favourite is Even ground, seeing as i mostly do everything in game i am always a few levels above the main quest content late in the game. It used to remove some of the challenge, now its finally "fixed".
Grizzly End - love it, bears are the real villains in this game and the most fun enemy to fight.
I could see Travel Light as something i would use, mainly because after having played the game for 600 hours i know where each cache is, so i can plan my potions accordingly. Would mix it up abit if i used this.
Rub some dirt on it - Not interested in it, it feels like a complete nerf. Though it would force the use of more potions and tonics in battle.
I do not like Take it slow as i usually find it takes awhile to get to level 27 anyway. I normally reach it at the end of Jaws of Hakkon or The Descent.
I did a short playthrough with Even Ground - Take it slow - Fair Weather Friends and - Travel Light - just to get the achievements, stopped after i reached Halamshiral. Was fun enough, but i would never do a playthrough without doing everything in the order i am used to.