"What makes you think that they may have a noticeable impact?"
Forgive my ignorance, a simple
JUnit test answered my performance questions. I have not observed any performance impacts using jarjar.
"I'd still have to recommend fixing the underlying issue, though, rather than jumping through hoops to fix it poorly. "
I completely agree with you on this; however, I am in a situation where that may not be an option due to business constraints (i.e. time and money). Thanks for all the great replies!