We broke one at our district championship event. The interesting and slightly concerning thing is that it wasn't at a particularly high load, just a sustained, consistent torque load due to a misaligned limit switch. The gear that failed is driven by a PG27 with a 16t steel gear on the output shaft and is only driven at partial power.
Unfortunately there isn't a steel option like these:
http://www.vexrobotics.com/vexpro/mo...ore-gears.html
We only use a portion of the gear's circumference to actuate our intake, so rotating the gear is an option we'll likely pursue at champs if we have the down time.