You are kind of throwing the dice each time you put out a strutting decoy. Sometimes they come running in, sometimes the go running off and sometimes they come in but keep their distance. They generally work better earlier in the season when gobblers are still establishing dominance. Later in the season they will scare off the gobblers that got whooped in a fight, but will still work on the dominant bird.
They are really just another tool, sometimes they work and sometimes they don't. The skill lies in knowing when to use them.
If I were strictly a bow hunter, I would definitely get one.