The Missed Triggers project identified this one as generally detrimental; the trigger denies you a resource, and makes you cast it all over again.
It can be argued (and it has been) that this also “fizzles” the opponent's spell or ability, thus making it hard to get rid of, and therefore it's a good trigger. In my view, that benefit softens the blow a bit, but it's still detrimental. Something as innocuous as
Amoeboid Changeling makes the Scourge nearly useless. In my book, that's detrimental.
d:^D