I was a product of very young orthodontics... I don't think it was a bad experience, but by the time I was in high school and still had braces, I was sick of them. I was 7 or 8 when I got my first few brackets on, and used a headgear to help align my jaw for the first year or so. I was 15 when everything came off, and wore a top jaw retainer for 10 years and a bottom jaw semi-permanent retainer for 5 years. I now have a nice set of straight teeth on top but my bottom jaw front teeth got messed up after the retainer came off.
I don't think the age has much to do with anything, but I do think that having the braces earlier is easier for the sake of getting it over with. It may be tough if you have a child who doesn't follow instructions, because if rubber bands are necessary, not using them consistently can delay removal of the braces. Not properly brushing and flossing teeth is a huge problem as well. Losing retainers will probably happen more in younger children, which will cost lots of money for mom and dad! I broke one and it cost $150 for a replacement at the time... nearly 20 years ago!
Best of luck with your decision!