I'm with Kayty.. I myself have never used them, but I don't class myself experienced enough to even touch them.
I got on a horse I was trialling to buy, and he threw me off from pain that I didn't know about(from a walk, all we did was turn left and he errupted). Turns out, I was told afterwards that the daughter "schools all her horses in draw reins." ... Well she had ruined his neck and it hurt him to turn the wrong way. He was actually put down because his neck couldn't be fixed by anybody. (I'm in no way trying to put her down or anything, I know accidents happen, but that incident scared me out of even thinking about using them, because when I was launched off his back, I was really, really launched and ended up in hospital after.)
-Not at all saying that you will ruin your horse by use of draw reins, and I'm not against draw reins.. Just sharing what can go wrong if used incorrectly is all :) don't want anybody getting hurt like I did!
I also know of a pony with an "upside down" neck because they schooled incorrectly in draw reins(I didn't even know that was possible O.O).
-Are you able to get your horse on the bit without them? If so I would opt for that, because chances are if you can get his head down with draw reins, without forcing him, that you should be able to get him down with normal reins too. I'm schooling my 7yo ottb with normal reins, but lucky for me he's a fast learner.
R.I.P ~ Bubbles - 25yo tb mare - 13.04.2011 ~ 8:30am ~ passed away naturally and peacefully in my arms