At our dojo Hakamas are worn from 1st Kyu (Black Tag) and above. We have a Black belt (of which nth Dan I am unsure.) who chooses not to wear a Hakama, and several others who do.
To someone such as myself, only just preparing to take a first test (7th Kyu), the Hakamas are an obvious sign of, not superiority, but of supervision, and experience. Not only are they quite magnificent to look at, and watch as the sweeping movements simply flow through the billowing Hakama, but they add a grace that is simply missing from simple dogi trousers.
I find that the Shodan(+?) who chooses not to wear a Hakama, looks more of a streetfighter, than those who choose to wear them. This is by no means a bad thing, but for an art that uses fluidity, and the aforementioned sweeping movements, and all, the Hakama without question, adds that special something.
I'm sorry I couldn't add anything further, as obviously I've never worn one, only observed those around me, but several things are for sure;
i) I haven't seen anyone trip
ii) I await the day when 1st Kyu may arrive, and I too can find new graces, responsibilities, and make those cool swooshy noises