I agree with Saturnus. I did have the view that they were a bit useless and pathetic, but sent an army into battle against an enemy possessed of a couple of units. They made mincemeat of my light and medium infantry and successfully dealt with hobilars.

I now use them as a kind of useful light infantry, keeping them in blocks three deep just behind archers. When the archers are charged down, they retreat behind the handgunners who let fly then can melee. I find them better on defence against units without a great charge bonus, when it does tend to scatter them. But they are cheap and can rout quite successfully (Armenian so-called 'heavy' cavalry seem a prime target for routing in this way).

So roll on handgunners, the undiscovered unit