I started a new fort in .04 and decided to give magma smelting a shot. Managed to keep everything walled off and secure (Even avoiding a flaming blob, that strangely entered the map with red body and two missing wings). So I thought I had it going pretty nice, and then goblins attack up top. I was still in the process of getting my military armed (as you can't start out gradual or you end up playing grab-arse with the arsenal dwarf and finicky dwarves who don't want to drop cheap crap). So they kill about three dwarves on the first few swings, send the rest running. I give the burrow call and find a new arsenal dwarf (who died in the assault). I've a full squads'worth of masterwork copper mail, greaves, and caps with some silver warhammers and a few steel spears. Should do the trick if they can just equip it..
And then the goblins run over my weapons traps as they descend into the fortress. None of them suffer any damage. They stop for a minute, then run BACK OUT through the traps. Again nothing. They head through again, to and fro, back and forth. I look at the records and the Green Glass Axes I'd mass produced are glancing off their silk gloves and caps.
Lesson: Don't use wood/glass or even metal traps without considering the new weapon properties. It's at this time I really wish lead could be forged into spiked balls, and that I had the steel available for blades. I'll re-equip them after it's over. That is if my fort survives the temper spiral, which is severe. A dwarf is being chased by his comrades as we speak. He seems to have picked up a dog and is flailing with it in a threatening manner.