I feel the same as Adrian, it's about a 50/50 deal-
If you dont have em. you'll wish you did at one point or another. I dont always use them, but ALWAYS carry them-Like Adrian said sometimes they work and sometimes they dont- If you can get an early set up or have time and cover to place them, then 90% of the time they work-
If your asking, I would bet that almost every avid turkey hunter carries them in his bag!

Hen and Jake combo usually is the ticket!