I think the loud sounds make it cool.
When I am tunneling and i hear enemy tunneling too I stop when he stops. Makes it interesting not to blow your cover.

I think we can hear digging from a bit too far away- so many times I've thought an enemy was digging under our intel, only to realise it was actually a friendly digging about 60 blocks away over a hill.

You can generally determine whether it is friend or foe by pulling out your map and looking for the friendly white circle. If there is not one present in your area, then you should probably begin searching out the enemy or running for your life like a little...ummm...yeah, but anyway, there you go :)

I find it annoyng that I can hear footsteps or building sounds from almost the other side of the level. It makes it much more confusing to walk around. You can't hear if an enemy is close or a friend is just building at your base. please fix the quality of the sound.