With most of these bargains, I feel the real penalty is loosing the feat spot. That said, these, for the most part, seem more like abilities a true demon would give you, more like a cursed gun that only shoots your foot, but doesn't tell you for their pure enjoyment.
Now a bargain with a devil is more sell your soul at the crossroads to play guitar type of deal. There's a quality you give up (partially) that's permanent for this life, and you get the ability free to use without further suffering.
Touch of death bargain seemed to mostly have that concept, but the rest were just using cursed weapons with the joke on us. And that's the difference between the devil and a demon.