So, how big of a deal is this change? Not a big deal -- if you are a TBM. In order for this to be a big deal, those in the church would need to recognize, or believe (Admit? Own up to?) the claim that women have not been privy to such councils before.
They have. This isn't a change in the practical doings of the LDS church. It is a subtle rewording and clarification of church policy (not doctrine -- there is a difference). For some, it is huge, it's affirmation and acknowledgement in a world where words count a great deal.
For others it's kind of like finally admitting that Tim Conway is a regular cast member of the Carol Burnett Show after three years of "special guest staring". I never understood why Carol was having Tim sign her autograph book at the end of another show - again.
Please. He was there every week. The only thing that changed was the title on his door and possibly his paycheck.
Women can have permanent seats on the council. Good. There was a place for them before. Good as well. They have always had a place locally. Ward councils include leaders from the women and the young women and the primary.
The times, they are a changing. Or are they?
Here is an interesting quote on he subject:
"But we can’t tell the story of women’s expanding leadership two ways. We can’t insist that women have always been empowered while also declaring that their new roles are wholly groundbreaking. In fact, when we try to do that we remove the very reason that yesterday’s policy announcement made history: It’s major because we have not involved women in leadership enough in the past. -- Jana Riess
Most people don't understand this issue; that there is a learning curve when humans are involved. Yes, the LDS church is the Lord's church. However he teaches correct principals and lets us govern ourselves. Mortal men, and an increasing number of women it would seem, who are attempting to govern themselves with heavenly direction. But it is still self, voluntary government.