It is very significant and almost (actually, to my knowledge completely) unprecedented. The next move by the defense will be a motion to have Nifong (spit) pulled from the case based on the ethics complaint.
I believe the state bar had previously said they would not look at this situation until the case was over, ie charges dismissed or a trial completed.
I suspect the state bar has been under a lot of pressure recently to go forward with the filing. Their main concern may have been to redeem their own credibility.
Something else that may have been a big factor in their decision is the talk from state representative LaRoque (and perhaps other movers and shakers responding to pressure) to enact legislation giving the state AG the authority to take steps against prosecutors acting illegally. The state bar would likely see that as an erosion of their authority (and ability to protect their own) so they acted because they didn't want to continue the feet-of-stone appearance that was surrounding them. In other words, their step taken at this time may simply be motivated by self-preservation and self-interest.
The next move by the defense will be a motion to have Nifong (spit) pulled from the case based on the ethics complaint.
This may be the plan all along, providing cover for Nifong with his black racist buddies and making an ADA take the fall for dropping the case.