I will base my answer on what has happened in the years as women have gained a stronger presence in the armed forces. One of the main issues is continued and overt sexual harassment, even rape and intimidation in some cases. It's been a huge struggle for many women, and some choose not to speak out so the problem is much worse than what's being reported. I think that sexual harassment would continue to escalate as women serve in more roles.
One misunderstanding that many Americans have about the military is that they think that women are excluded from many positions. While it is true that women currently cannot serve in combat arms roles, it is untrue that they are not in combat. Many women experience combat if they are MPs (military police officers), part of transportation units, etc.
While there has been a great deal of talk about women serving in combat specialities, I have heard or read nothing about how many women who are currently serving actually want to be in combat MOSs. Serving in the infantry or special forces would mean that women would have to be able to perform all the physical tasks at the same level that men perform them in combat. While many women claim to be able to do that, it is interesting that the military still has different physical training standards for women and men (longer times for women to run, fewer push-ups required, etc.). While there is talk of the military developing uniform physical standards, that has yet to be done.
Another detriment to women serving in combat specialities is the cost that would be involved. For example, the current situation in Afghanistan requires that many combat arms troops stay on remote FOBs which do not have separate barracks, showers, etc. Does the U.S. have the money to provide separate quarters for women? Similarly, do most of our military women really want to stay in areas where they might not be able to shower or maintain personal hygiene standards (which are obviously different for women than they are for men)?
Personally, I would like to see those who are serving or who have served make the ultimate decision about women in combat roles. Very few of our Congressmen/women and Senators have served, and yet they will make a decision (as it stands now) that will not directly affect them.
Very difficult question. I guess there have always been separate rules for the armed forces because people chosen to join the armed forces have a role to play that differs in several ways from even those with similar professions in other organizations.
The kind of conditions that people in the armed forces have to fulfill their duties under are a lot harsher. Not that women are not tough or can't play the role that men can. They may even turn out to be better that men, but one can't just look at aspects like equality of the sexes to make decisions here.
The first effect of this law would be (if this is your view) that the US would be a more just place. Women would no longer be excluded, solely on the basis of their sex, from jobs they were qualified for.
On the other hand, there are many who think that such a law would harm the armed forces. They argue that, for example, women would be much more likely to be unavailable for duty (due to such things as pregnancy) and that this would reduce the force available to military. They also argue that it would degrade unit cohesion in combat to have men and women serving together.