Myself, I try to avoid using them whenever possible as they remove a lot of the challenge from DF. And there's always the fiddly and awkward process of disposing of what's in the cages.
I was playing with cage traps and using the captured gobbos as training dummies. The first siege brought the Goblin leader, who was helpfully captured in one of the cages, leading to a glorious project. The mass pitting room was expanded to allow 72 things to be chucked down into my militia at once, and a small side VIP box was constructed for the Goblin leader, with a perfect view of the slaughter through fortifications.
The games begin, and the first round of a dozen thrips men is killed quickly. A handful of stripped goblins are released next, and slaughtered. Then one troll, then two at once. Finally, a whole squad of goblins who were allowed to keep their equipment are dumped into the militia, and they were cut down. No significant injuries other than one death of a recruit who apparently forgot to pick up a helmet. The doors were unlocked, the militia returned to their barracks and booze...
...and then the entire fortress descended into the arena to pick up the corpse (or maybe the goblins' socks), froze in terror at seeing the goblin leader in his prison, and ran away only to stop, turn around, and do the same thing. Turns out I forgot to build the drawbridge shutters for his prison. It only went on for a bit, but having every civilian in the fortress parade into a miasma filled pit decorated with dwarf brains put me smack on the rails for the tantrum spiral that killed the fort a few game months later.
So yeah, I would also recommend a dodge trap or a glass serrated disc trap.