I have never worn a hakama myself, but I have had at least 10 accidents when my foot or toe got stuck in nage's hakama while being thrown. At every time, I avoided very serious injury by a hair's width.
I have seen fresh yudansha frequently stumbling into their hakama and falling ridiculously, for at least the first few months. It is not unusual to see 3 dan and 4 dan teachers stumble in their hakama from time to time. I think accidents are inevitable unless you wear your hakama at knee level or slightly lower
As for hiding the feet, yes it does, and this is the purpose of wearing it. In our dojo, there is great emphazis on correct posture and footwork, so I guess the hakama will get in the way towards achieving good and quick progress.
By the way, I've seen at one dojo beginners wearing hakama, and there was not so much grace and elegance ....
At our dojo, after 1 kyu, you have to pass a shodan ho test, which basically is a probation period for black belt during which you wear a black belt but no hakama. If you pass this period successfully, usually after 1 year, you have to pass another exam for shodan after which you will be allowed to wear hakama.