Just wanted to share my experience...
I have long avoided riding in spurs. I would NEVER use them to get forward in a horse. I strongly believe in better training instead of spurs, whips, etc. However, I have started showing my ASH, Bundy. For a working ASH class, I need to do stops, rollbacks, haunch turns, as well as cracking a whip, etc. He has come a loooong way from when I got him, and has been placing consistent 2nds in our recent working classes. I made the decision to try him (and me!) in spurs, to sharpen him upp off my leg cues. In other words to sharpen up his response and response time to my cues for things like rollbaks and haunch turns, and to fine tune my aids, as he can sometimes be a bit sluggish.
So, I bought spurs. Similar to this:
(I'm a firm believer that rowel spurs (smooth ones) are milder than dummy spurs)
I do know that bunday had been flogged with spurs in the past, so I was very wary and gentle.
The first time I rode him with them, I only had a short ten/twenty minute ride. All I did was put him through walk/trot/canter on both reins, a few stops, and a little bit of side pass at a walk to get him used to moving off the spur.
To begin with he was putting his ears back and throwing his head when I used the spur. (I was only using it very slightly to cue transitions. Otherwise I was using my calf to apply leg pressure as usual) I figured he was anticipating a jab as he has received in the past. He eventually realxed a fair bit as he realised I wasn't going to beat him. He did keep jumping into a canter at the slightest leg pressure, but I believe that was part of him adjusting.
Anyway, in a couple of days, I was riding him for a full day doing cattle work. I used the spurs. He continued to relax more and felt less tense. I was also practising finding the exact point where the spur met his belly and fine tuning. I admit I did accidentally spur him once, I asked for a stop and he stopped far more abruptly than I was ready for! My leg tipped back and I did spur him, lightly though. Only time that happened.
Anyway, the point of this post. It really helped with his rollbcaks/haunch turns when working the mob. And the absolute highpoint: On my way back from the yards to where he is kept (20 min ride) I asked him to collect and perform like he would at a show. And WOW. He lifted his back, engaged his hind, and absolutely powered up the hill in this amazing forwad, bouncy, round trot. (we took a long time to get the concept of forward in a trot) I asked for a canter, and again, wow. Lovely steady, collected, bouncy round canter with a lovely lifted belly/back and engaged hind. It was amazing to ride...
Just wanted to share my GOOD experience with spurs!