The Best Answer
Like normal peanut butter, you'll have to limit yourself having it in excess. The fat content in it is good fat, but it's still fat and there are a lot of calories attached to each serving. With that said, I would stick to no more than about a tablespoon (half serving) to a full serving per day. Even then, if progress starts to slow, you can always just not have the peanut butter. I hope that helps!
I just purchased some last night for the same purpose (celery and peanut butter, yum!)
I did verify that there was no added sugar (... and it is suprisingly difficult to find peanut butter without any sugar at all). I searched the blog and found no conclusive answers about peanut butter, but I figure it can't be any worse/better than almond butter. I would use it sparingly because it does have a lot of calories/fat, but a tablespoon or so once a day seems reasonable to me...