I personally love using hackamores when you can. I have bridles with all sorts of bits, bitless bridles and lots of different types of hackomores, and I use all of them regularly for different purposes. I ride a Paint/TB cross gelding, and he's got quite a bit of spunk when he's not with the little kids, but we tried a bit on him and he just hated it. He leaned his head to the side, trying to get away from the bit, and sometimes just flipped his tongue over the bit and ran away. But I use a Mustang-brand braided hackamore or a rope hackamore, and he listens like a dream, I don't even need to use rein, he just moves off leg and neck-rein aids. Two little Exmoor ponies we have go in Nurtural bitless bridles, and respond perfectly, but they don't listen with bits.
That being said, my own Arab mare won't listen unless you have a bit in her mouth. She just feels secure, I guess, because I can drop the reins and she'll listen to just leg, voice and seat, but if I do that without a bit in her mouth, she won't do a thing I ask her to do.
So by all means, go for a hackamore. I reccomend bitless bridles as a first step before hackamores though, because they're just like riding with a bitted bridle, but all the presure is on the nose instead of in the mouth and on the nose, so it's easier to get used to for the horse. It's hard to explain, but that's just what I reccomend :)