I still don't get why everyone's upset about Banette not being able to KO itself to place 8 damage counters onto the defending...self-KO always seemed like a dumb move to me.
Anyways, Banette is a solid card, best used for a T2 deck or something. 80 HP is average, +20 Weakness to Dark isn't as harmful since the only decent Dark Pokemon even used for attacking is Honchkrow, -20 Resistence to Colorless is wonderful for Blissey matches, and a Retreat Cost of 1 is typical. Ghost Head, with its new errata, only lets you place a maximum of 7 damage counters onto itself and the defending Pokemon. Granted, you now can't kill Banette to (presumably) kill the opponent's Pokemon if they have 80 HP left, but for being a free attack, it's decent still. Spiteful Pain does a solid 40 for 2 Psychic energy, but if you have a Banette in your discard, you can shuffle it back into your deck and deal an additional 40 for a total of 80. The only problem I see with Banette is maintaining this damage consistently, but I guess it's possible.
Modified - 7/10 (Still useful for G&G and Blissey match-ups)
Limited - 5/10 (Decent Stage 1, but not being up to its full potential since it's unlikely you'll get 2 or more Banette)
Unlimited - 1/10 (No use here)