I've only ever gone to one chiropractor, my dad who has had a long history of back problems referred me, and the guy was really good and caring. As far as chiropractors are concerned, he's probably grade a. But whether or not the cracking the joints stuff is actually good, I have no idea.
Then again, when I work out, especially sit ups and stuff, I always crack my back, simply out of necessity to be able to carry on. I've been actually taking a step back to much lighter exercises to try to build up the muscles, especially bridging and lower level leg lift exercises, but it is a process. In any case, the fact that I crack my back to make it functional in workouts points to that there is some merit in it. For the long term, I don't know.
My dad always said that yoga is the most effective. I also think that the building up the muscles thing, along with yoga, is probably ideal. But if you don't have time or patients for it and want to get some relief, and be able to move and be functional, than perhaps a chiropractor is a way to go.