Adjusting in war: Have we adopted any enemy tactics over the last decade?

I
was enjoying a Sierra Nevada Torpedo or two (yum-oh) and reading The Complete Roman Army and
this line jumped out at me:

It was a point of pride for the
Romans to be willing to copy and employ the effective tactics or equipment of
their enemies. . . .

This
made me wonder: Have we copied any enemy tactics over the last decade? If not,
is there a good reason (like the tactics are inhumane) or is it just the "casual
arrogance" that Andrew
Exum identified?