I've had one and there was no damage because I hit the Estop at the same time it was crashing. I've only been running about a month or a little less though. I generally cut small parts out of small sheets too, so I watch the machine the whole time.
If you use larger sheets, I would say do it for sure. Then you can have some peace of mind and walk away a bit and don't have to hover over the Estop button.
I still plan on designing and installing one on mine. Torches are not cheap and a breakaway is fairly cheap insurance.