I have fished in lots of timber. I have no issues. I just go slow and bump them along the way. Like Shaun says, I keep my middle tab unlocked so when it hits something it pops the shaft up. But like any other prop, if you hit something hard enough it will break. I have not broken mine, but I have witnessed a buddy break his and he was right next to me. I now carry an extra prop just incase. He was able to finish out the day fishing, but he said it felt awkard and a dramatic loss of speed.

I would think that since it's driven by leg power you won't go peddling full speed into stumps and trees if visible, and even then you would not power your way through bumping logs and knowing you don't have a stainless steel prop, because that would be just asking for trouble. Maybe something that Native needs to consider.
It's still a kayak, so you should still be carrying a paddle just in case plus the extra prop.

I'm still a big fan of the Slayer Propel, and it's on the top of my new kayak list.

I've been using the Slayer Propel for some time now, and it's simply awesome!!!! speed , deck space, storage space and comfortable . the reverse is a added bonus for me when it comes to holding your spots on windy points. Native is doing great things!!!!