"1-2 hours on the trail makes a new man of me.... every. time."
FreeOwl - I can definitely relate to this. an hour and a half to two hours is my favorite length of run, and definitely on the trails. I ALWAYS feel better after this.
SoberRunner - I mix it up, half the time I'll listen to music, and half I don't. I think I get the meditative effects of being out on the trail more when I don't have music, although when I do listen to music it often empowers me and gives me a different type of positive experience, depending on what I'm listening to.