I'm in the end of act II (inferno) and have found it to be a really outstanding combination. Spike traps do a lot of damage (275%), and if you rune it with 'Scatter' you'll end up with 3 traps. With a little micro that's 825% damage to a single target and the price is not that high: 30 hatred - it works even better on mobs; the total damage gets easily way over 1000%.
But if you use caltrops with 'Bait the trap' it works even better. Standing on such a caltrop gives you 10% extra critical hit chance - so, the 275*3% damage has a high chance of being a critical hit. Playing with good equipment and the 'Sharpshooter' passive ability pretty much make at least one of the traps being a critical hit.
The shooting you're doing while on the caltrops also gives a 10% extra chance. On a side note, when the enemies reach your caltrop they're slowed for 60% speed in 6 seconds.
What are you guys thoughts on this? Ever tried it?
This is my build: