Re: who can wear hakama
In our dojo, only the yudansha wear a hakama... I'm not sure about the women, but for as long as I have been a member of our dojo (7 years) I haven't seen any women wear a hakama unless they are shodan or above... The only exception to this is that a yonkyu and sankyu at our dojo teach the children's class, and they're allowed to wear a hakama.
I know that traditionally everyone wore a hakama, but frankly I don't see a problem of wearing it only after you get your shodan... It gives the students something to strive for, and I know that even though I feel an accomplishment after every class anyways, I look forward to wearing a hakama one day (i'm ikkyu at the moment).
Also, it helps beginners tell apart the seniors from the juniors, and usually the yudansha are more experienced than the mudansha, so if the beginners have a question to ask, they can ask the seniors... and although you should practice with people of all abilities, usually it's better if a beginner practices a technique they've never done before with a yudansha first so they understand the correct movement. (i know that was a run on sentence)