This was hottly contested sometime ago. The Sage said that during your turn, you can use the partial action from haste or the extra attack from a weapon of speed, but not both.Caliban interprits it to mean that you cannot use the benefit from a weapon of speed _during_ your partial action from haste. His reasoning is that as the weapon of speed description stands, you can benefit from two weapons of speed in the same round, but not from a weapon of speed and haste spell and that doesn't make much sense.
I think that sums up both sides of the previous arguement. For the record, I'm with the sage on this one. The intention is that you can't use weapon of speed and the extra partial action from haste in the same round.
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