If I ever draw an archery antelope tag, I'll be getting the antelope version of the be the decoy. I saw an On Your Own Adventures episode where they had multiple stalks go really well with that hat, and it seemed like a useful tool to have in your arsenal. I'd be a little nervous about using the elk version, though, as I've heard of two people now who have had their elk decoys shot at during the archery season, and it seems a little risky to me.
I personally use the Montana collapsible cow elk decoy and it helped me get my bull this year. I just set it about 20 yards to my right and maybe ten yards in front of me. The bull was initially coming straight in (because I was calling solo), and he saw my decoy, and diverted toward the decoy to give me a 35-yard broadside shot.
I've also wanted to try the bow-mounted decoy from ultimatepredatorgear.com. It isn't the full body of an elk, so I think it would probably be less likely to get shot at than a bigger version.
I think having a decoy can be very beneficial, especially if you generally hunt alone like I do, and it paid off this year for me.