There are lots of them in the military. As far as I know, there are still none in the infantry, artillery or armoured roles (maybe Field Engineers as well) in the regular forces but there are in the Militia. But that's more a moral issue than whether or not they can do the job.
I had allot of women working for me when I was in the Army that I'd chose over some men any day. If you had made the sandbag comment to one of them they'd either give you a look and start planning on where they could dispose of your body or tell you where to put the sandbag.
There were also some women that wouldn't be my first choice for a job either.
I think that what it comes down to is that you can't paint everyone the same and whether they are male or female everyone is going to have their strengths and limitations. As long as the person can do the job, it's all good.