I'm also a huge fan of the PB! My morning protein shake consists of a cup of nonfat milk, 2tbl PB, chocolate protein powder (maybe a tsp of sugar free cocoa powder for some extra chocolately taste), and about half a banana (sliced and frozen). It's absolutely delicious! I get the smooth creaminess of the PB, plus the chocolatey flavor, and there's the banana too (frozen fruit helps make it thicker). I feel like I'm having a regular milkshake for breakfast. I get PB and don't feel like I'm missing out on sweet things.
But as for PB killing my diet, as others have said...moderation is the key. And I can't ever just sit with the jar, I have to measure it out and put the thing away.