Okay, my humble little opinion on this:
Many people complain about getting caught or tripping in their hakama. I personally have never had such problems on the three separate occasions I have trained wearing a hakama. Even while working on some suwari waza techniques.
Length is everything. A longer hakama certainly does present a certain threat. The rule of thumb that I have been taught (granted I've been making, tailoring and dealing with Hakama's for a few years now) is that you should at the very least be able to kneel in a semi low position ( i.e. as you duck under your partners arm for certain techniques and ect,) with out the hem of the hakama getting in the way. I noticed in both the seminars I've been in that most people had their hakama's hems about ankle length or higher. As to suwari waza I just tucked the sides of the hakama into the vents. Funny looking yes... functional? Yes!
All in all its a personal preference.
For me I stick to tradition. However I do not care very much for the hakama being used as a "gift" for being promoted to a Dan rank. Ranking in its self a large gray area and should not be treated in such a manner, IMHO. I believe in fair treatment for everyone, and am lucky enough to be able to train with a group who does not judge my lack of rank, but on the spirit and energy I put into my training. I am respected and I have grown farther then anyone thought I could in this short amount of time. Hakama or not. Belt or not. I wish this kind of thinking is more wide spread.
Personally, kyu, dan whatever I think wearing the hakama should be a choice. If it becomes detrimental, don't wear it. Just Train. Isn't that what we come to the dojo to do, when everything is said and done?
Sorry if this sounded gripey. Just one of those things I've got a strong opinion on..
The kyuless one
(but not so clueless anymore)