You would.
IMO, you should be aware of any immediate penalties, bonuses, and what not, unless it's some kind of "quiet curse", and since this is a 1 round effect that accompanies what is likely an attack spell, it's not a "quiet curse". Furthermore, you're not likely to "not bother" to cast spells, because no one is likely to cast a disruptive spell on you outside of combat. You're fighting to survive, and your best tools are spells. Even if you want to cast Dimension Door and just run away, you still need to make that check.
Maybe if you're a magus you might just rely on your sword until that round has passed. Maybe if you're a cleric and you've already partially buffed you won't cast any more spells and will just bash your opponent's face in. But quite often this metamagic would be useful.