it depends really on the person who has them. mine was painful, but then again, the dentist did accidentally managed to get my wires to the top two front teeth into my gums, which put me in pain. the tightening itself was enough to make me cry at 16 to the point where the staff at the group home had to heat up a cloth, pad, or rice sock to get me to go to sleep cause the pain kept me up all night. also because mine pulled my teeth up to the front, and at the same time i had a wisdom coming in, so that only made it worse for me.
but, if you get a gentle dentist, you'll probably be alright. i had a dentist who liked the old fashion ways, and now braces are put on different then what he had done.
Annoying and seems like forever before you can get them taken off, but well worth it in the long run.
it hurts at first then you get used to it