I took my ex-racehorse Bapsford bitless first several years ago, he always had a tendency to fight the bit, made worse when I was told to use tight nosebands to stop him getting his tongue over. In the end I had him in a Myler snaffle with loose cavesson which was the best he was bitted, but then I discovered an article about a lady team chasing in a Dr. Cook bridle and decided we should try one of those - I had no idea until then that such bridles existed, I had only come across the traditional English hackamore which didn't ever appeal with the leverage. After 5 minutes testing the Dr. Cook in the school I was happy that Bapsford understood the aids and, better than that, was so much more relaxed - we were off down the road and cantering around the village green straight away! He became so much easier and less spooky, we both gained confidence and our relationship (which was never bad) improved hugely. We completed several fun/sponsored rides bitless and I jumped more than I would have dared previously as I didn't have that awful out of control feel. We competed in 2 full Trec competitions and several arena Trec competitions and were always placed and often it was commented how calm he was for a thoroughbred!
Sadly (for me, not him!) he retired November 2013 after riding with William Reddaway and Strider on their Ride Round England, but he is a happy in charge of his herd.
After the success with Bapsford I decided I wanted to get rid of bits altogether - I don't think I have ever liked having to put metal in a horses mouth and then 'pull on the reins', but you are made to feel that it is ok because we have always done it. It was very liberating once I had realised I didn't need them and started to convert Magnus, my Shetland, to bitless. This took me a little longer to be sure we were ok as I was driving him. But he responded well to the Dr. Cook too (after one initial hissy fit when he tried to yank the reins and it hugged his head). He became more relaxed and pulled/yanked on the reins much much less. He has completed a long distance drive, several group BDS drives and a BDS Trec competition bitless (and barefoot).
With Bapsford retired it became time to start Monkey, my young Connemara that I planned to start and bring on myself bitless. I have mostly done agility and relationship training with him, nothing very traditional. I first sat on him Dec 2013 then gradually started riding a bit over the summer last year, now we are hacking and have just started a bit of cantering! All in just a rope halter and now side pull -I have modified my Dr. Cook - so far so good. Sometimes steering goes a bit out the window if he is distracted and not listening to me, but when we have our connection he will go from my weight and leg aids and stop with my breathing. He has taken part in 2 arena trec competitions and came 4th in his first one!
Finally I have Fraoch, another Connemara but one with history and baggage. Prior to arriving with us, he used to rear and bolt when ridden. He is coming on well and is ridden in either a rope halter at home or cross-under bridle when out. No rearing or bolting since being bitless and he is gradually starting to relax and enjoy hacks out.
I've ridden various other horses for friends in my bitless bridles and only ever had positive experiences with the horses quickly understanding the aids and being more relaxed than usual.