There may be a bug with them in the current prereleases, though they are fine in 2.0. This is on my list to look at in the next week, before we put out the next official version. What they are supposed to do is provide 100% protection from incoming sniper fire to anything in their protection radius. Note that the protection is conferred when the enemy shot is fired, not when it arrives -- a counter-sniper flare is sent out when the enemy shot is fired if the protected ship is in range of the counter-sniper, and then the counter-sniper flare hits the enemy sniper shot and kills it. Possibly the sniper shots are too fast now, and the counter-sniper shots aren't reaching them in time, or something like that, but I'll have to look at this more in the next week. I have a savegame from someone else that I can use to test this.