I've always been of the opinion that the military/government/corporation/whatever should judge a person based on their ability to fulfill the position. If you dismiss someone from a position because of some basic quality of their identity, whether it be sex, race, educational background, etc., you're an idiot. It doesn't matter if only 1% of women can complete the fitness requirements for battle. If they pass the test, they go on the front lines. Simple as that. Keeping someone from a position just because of who they are, even if they are perfectly capable, is plain stupid.
The bulk of the arguments coming against this decision were of the "women are not natural warriors" and "women are not as strong as men" variety. Both are true. On average, women are significantly weaker than men. Men tend to be more physically fit, and are generally better at enduring the physically demanding environments in battle. That's why men have chiefly been the warriors in historical societies (that and women were often pregnant, replenishing the depleting population). In modern times, when physical strength is less of a factor in combat, and when qualities such as marksmanship, leadership, intelligence, and tactics are more valuable than brute muscle, these arguments hold less water.
In other words, it's about damn time America. One small step towards rejoining the rest of the modern world.