OP you never said what you thought? Though I reckon by starting the topic, you'd say they are legit?
Ah, but that was intentional
I didn't want to start the discussion off with my own bias polarizing the matter, but rather wanted to see what people's baseline thoughts were first. Unfortunately, your assumption is incorrect. I am actually rather opposed to the ideas and practices of chiropractic (to answer your question, I made the topic because my girlfriend's primary health care practitioner is her chiropractor).
In particular, what I do not like about chiropractic is it's very shaky foundation, it's facetious teachings (bold to say, I know, but I'll get to that), lack of empirical evidence, and it's generally strong opposition to modern medicine. I'll use that as an outline and try to keep this short
Firstly, chiropractic was founded in 1895 by D.D.Palmer, who was a magnetic healer, after claiming he cured a deaf man by a carefully planned adjustment (which in reality the man wasn't deaf and it was an accidental slap on the back rather than anything carefully planned, as claim witnesses). Pursuing this avenue, he built the basis of chiropractic, which is that any disease or ailment known to man (from small pox, to heart disease, to deafness) can be cured by "spinal manipulation". He believed that nerves transmitted energy to organs and other parts of the body, and that by misalignments those pathways were pinched, which caused organs to fail and sickness to occur. He was the one to come up with the idea of "spinal subluxations" to describe these special types of misalignments. He eventually opened up a school as an extension of his magnetic healing practice, and after a long list of other mishaps I won't bother listing, he passed it onto his son, who took things further and at one point considered making chiropractic a religion.
Fast forwarding to today for the second/third point, straights and mixers both teach and follow the original beliefs of these "spinal subluxations", despite the fact that they have no formally definition even among chiropractors, and x-rays and other modern medicine techniques (plus our better understanding of the nervous system which contradicts Palmer's claims, and thus the basis of these subluxations) can't even prove that they exist, let alone what they are. In my own personal experience, I've gone to multiple chiropractors who all told me I had spinal subluxations, but each said I had it in a different location (and repeat visits to the same ones still claim to find them where they did the first time, so they aren't moving). The only logical answer then, must be that these "subluxations" are mythical entities, designed as a reason to keep you coming back week after week for the rest of your life.
Finally, and the real one that bothers me, is their grudge match with modern medicine. Almost every chiropractor I've been to have various materials (pamphlets, books, videos, etc) teaching about the evils of modern medicine, claiming it to be one big conspiracy, only caring for money and not for human health. While I agree that money makes the world go round and it certainly isn't perfect, to say such things basically implies that everyone going into a medical profession is in on this and evil, and if it were true I'm rather certain our lifespans would be getting shorter, not longer. Nonetheless, they use scare tactics (literally) to pull people into believing that they can cure you with their magic hands and practices, and medicine should be avoided. This comes personally to me regarding my girlfriend, who despite having little in the way of poor medical history, has her chiropractor as her primary health care practitioner, and I've watched over the years as her health has degraded from where it once was, and rather than going to specialists, her chiropractor tells her to go on different eating plans and other alternative means. There is also no way to prove or disprove if it's working, because if things don't get better, it's because they take time, and when they do, it's because it's finally working.
Bah, this was longer than I intended... I'm sorry... I do want to finish by adding that not everything modern chiropractors do is without merit (some branch into nutrition, or physical therapy, but both have specialized fields anyways), but in my opinion chiropractic itself has almost no merit. I've seen it hurt more than I've seen it help, and there's just enough fishy stuff about it to make me less than willing to give it the benefit of the doubt.