I love peanut butter. It is totally a stable of my diet and hasn't killed it. The fat in peanuts is monounsaturated, the "good kind". It is caloric, so I eat half a serving which gives me about 100 calories and 9 grams of fat.
When I eat foods that are higher in fat it helps control my blood sugar, helps me feel fuller longer and gives me more energy. I eat oatmeal with peanut butter and honey before I run.