trying out spiked conveyors in v1.3.1 and they're not hurting mobs at all.

Will look into it tomorrow. It's quite late here.

Nope - didn't know I had to. Instructions: "Spike Conveyor - Comes in 3 tiers. Damages mobs and holds them in place. 6 damage for Iron and Gold, 7 for Diamond. Gold also drops experience, and Diamond also drops player-only items and experience."

Description has been updated on the page, sorry for the inconvenience.

Works fine for me, are you powering the Spiked Conveyors with redstone? Are you on a server?