I've only been very, very recently introduced to these things, only yesterday in fact. I haven't really come up with an effective way to take them out, since I was playing in the early stages of the game and lacked any armor. My strategy I used to take them out was to charge in with a sword and shield and hope they don't kill me first. Worked okay-ish, but ended up with a scarred shield in desperate need of replacement. It was a bit hard, too, since there were three traps within a close proximity, all in a small stream, making it hard to get close to them. But, hey. At least I got an enchanted helmet and bow.
So I'd like to see your methods of taking out these traps. Do you use arrows? Do you do the same I do? Or do you set up some complicated traps?
My current base has water on nearly 3 sides, and most of my STH's have spawned in the ocean. Its quite funny to go up to a horse then swim away after the trap activates as the horseman are mounted for a few secs then become unhorsed because of the deep water. So they all just bob about. I find them annoying more than anything because I always want to try the all the horses out in case there is a fast one. I have been ignoring the more recent ones (they despawn after 15 mins). I did encounter one on land not so long ago in a tree, and that was my last MC death - they were really fast on horseback and I got pummelled.
Incidentally, will a trap go off if you're invisible when you approach? Not tried that yet.
A pic from a few days ago - five in the water near my Guardian Farm. I just left 'em.