I'm very happy with mine, but he is also a fully qualified equine vet who specialises in chiropractic work. Very well thought of, he hasn't taken on very many new clients this year.
I'm fortunate that I've been a long standing client, as he's tightened his travelling area up tho still comes out to me.
Mine is great, but again she is also my vet. Personally I think I would be less inclined to use a chiropractor that wasn't a vet. On the veterinary side of things, mine specialises in lameness and performance issues, and is also fairly involved in the dressage world. I find she has a fairly holistic approach which I like.
To use the title Chiropractor, you need to be a human chiropractor registered with the General Chiropractic Council, or a vet who has completed the IVCA course. There are Animal Manipulation courses you can take without the above qualification, but you cannot legally call yourself a chiropractor.
I used a chiropractor recently, for the first time. She has a human's clinic which is where most of her work is, I think. She continues to travel out to horses because she likes doing it, but it isn't her whole week.
I was at a yard about twenty years ago where the chiropractor would come out, we would line all the horses up for her to treat and in turn she would and adjust the horse's spines and say that every horses pelvis was out. I was too timid to really ask what she was doing to my mare and gave her the thirty pounds.
That was my last experience of equine chiropractic as I tend to use equine vet physios are my first port of call, but i wouldn't hesitate to use a Chiro if the vet thought it beneficial.