Orc Archers are basically regular skeletons, but better. They are more accurate and fire more frequently, which can make them very annoying, especially when you are being attacked by another mob at the same time. However, at lower levels (relative to the players level) they can be a very good source of expierience points. They also drop about two pieces of flint, a few arrows, and possibly a bow. They may drop other items, but this is rare. You will usually get common items off of them.
Orc Archers can be very annoying when there are groups of them, and especially annoying when you are being attacked by a mob that attacks close-range. This should not be a problem if you are a warrior, but if you are a ranger or mage, it can be dangerous. However, Orc Archers are relatively easy to dispose of at close quarters, as the bow is their weapon. Just make sure you have a sword, club, or other melee weapon at the ready.(You should probably do that anyways for Giant Rats, Nagas, etc.) Try to stay behind them and always move.They'll probably miss, and then you have a window of opportunity to attack them before they reload. Like skeletons, strafing and jumping frequently are always good strategies.
Their current sound is that of a zombie, though many players think that zombie pigmen sound files would fit better.