Don't you get just crazy sometimes when you insert that [Nebula program] on the overhead track and suddenly everything sounds weird? In a dense mix or adjusting in "solo" you might not realize it at first. Even worse, you will start to adjust the other tracks as well. Only because the polarity of one single program (or suite) is off!
My suggestion: build a database (sticky) with possibly all programs marked "+" or "-". Yay or nay?