We've house ruled it thusly -
Gave it a costly material component - a 100gp dram of quicksilver, rare in many places (read: where I don't want the PC's casting haste too much).
Interpreted the spell so that it takes effect immediately for the dodge bonus, but only confers the extra partial action if all of the previous actions in the round were hasted - i.e. no extra partial action the round you cast it. I wasn't sure whether this is the official interpretation normally, since it is not mentioned in the spell description or the FAQ one way or the other, but the common interpretation seems to be that you get the extra partial action right away. Not so in our game.
Gave it a costly material component - a 100gp dram of quicksilver, rare in many places (read: where I don't want the PC's casting haste too much).
Interpreted the spell so that it takes effect immediately for the dodge bonus, but only confers the extra partial action if all of the previous actions in the round were hasted - i.e. no extra partial action the round you cast it. I wasn't sure whether this is the official interpretation normally, since it is not mentioned in the spell description or the FAQ one way or the other, but the common interpretation seems to be that you get the extra partial action right away. Not so in our game.