95% of the time it's fine, an improvement even in the top special forces echelon (imagine how much easier it would to be all sneaky if you were a lady instead of a dude), I think that the "we don't want womens in the fox hole with us" is overblown and women already are in some combat positions.
...but physical and mental standards shouldn't be lowered to make it happen.
Though I would think it would be more of a physical issue. There's more overlap than you think in terms of whose dark, obedient and though enough for the job. However, its reasonable to think that where half of all men can probably be trained up to be strong enough, only 1-5% of women can be. Its very tough for girls to pullups, but out of every 10-20 I see in the gym, there is one that can do as many as a man.