I bought one in 2004 and tried it several times with no success at all. I did not see any purpose to continue. Did have a couple friends claim positive results. I can at least try it again next year I suppose. Should not spook turkeys.
The actual burning of the repellant will not spook turkeys - HOWEVER - the button to turn it on makes a noticeable 'click' and it takes 2-3 clicks to actually ignite. I've scared birds that were close (that I couldn't see) with the clicking, it's a very unnatural sound to hear in the woods. I either lite it at the truck and carry it in already on, or stuff it inside my coat and vest when I ignite it, to muffle the clicking the best I can...