ive had mine for about 12 weeks or so, doesn't hurt to bad, but i had to get an expander and that sucks!
did you know, they can just glue the
bracket band thing on you tooth so you don't have to get the spacers? ask about it if your getting braces soon, hurts a CRAP load less

Edit: I've got a crap load of work done on my teeth, so I was a bit nervous, but, its not all bad.
Example of work on teeth: the first time I went to the dentist, i had to get like 3 caps, or crows, or what ever you call them, and before I could get braces, I had to get a tooth uprighted and get one of my wisdom teeth removed for it to happen, so I hate the dentist... but braces aren't nearly as bad.
Edit2: I have to have mine on for about 16 months... D=