[Scottg]

..as long as your net attack numbers are very high then it should be OK. It's particularly useful when hasted regardless (OR Frenzied), because the additional attack that Haste OR Frenzy provides is at your top attack number.

The problem I have with the trade is -6 attack for +10 damage, NOT that great a deal (though in some circumstances not bad). At 10th level FB it goes to -6 attack for +12 damage.

-6 attack for +20 damage without access to a second weapon or shield is to me a better trade.

BTW, the addition of Supreme Power Attack works exceptionally well with all high damage melee classes.