So fans speculated Storm's choice for bring back the mohawk was stress related. That doesn't seem so anymore considering...
*possible spoilers ahead*
1) Divorce with Black Panther- Sure that was stressful for her, but she seemed to know their marriage was failing and to top it off, they decided to be civil again in A+X... Which is stupid, because they had some nice tension going on between the two. Not to mention her and Wolverine and making out on the upcoming cover of Astonishing X-men.
2) Xavier's Death- She doesn't seem to be grieving him much... She didn't even speak at his funeral, because Marvel made Wolverine do all the talking at that pathetic excuse called Xavier's funeral. She attended the funeral.
3) Scott, Emma, Magik, and Magneto's Fall from grace- Friends becoming outlaws can be stressful. But she is reunited with her old friends she hasn't seen since the x-split.
So... I ask again... why? It seemed Marvel had much material to work with to make it seem like Ororo has gone through very traumatic times- and the Mohawk & joining X-force is the physical manifestation of her current state of mind. She seemed broken, now they quickly patched her up and she is all smiley and happy in recent issues (With the exception of All New X-men). The dark look, attitude, and mohawk were supposed to reflect on how Ororo is doing, ...right?
(For the record, I like the Mohawk and X-force look. I always loved it, and I thought it looked best on the covers of Astonishing X-men: Xenogenesis.)