I have considered it, but the 'unfun' of 'wasting' a resource and having a bad roll for the DC kept me away. Making it an opposed roll {caster check roll vs opponents save roll} increases randomness.
Using the 4E-ish save mechanic would make this variant much more acceptable {caster check roll vs opponents static defence}. It also makes more sense as a high reflex character won't fail against a spell that a low reflex character saves at.