I've had about 10 flights with the foldable STO props.
There isn't much benefit except for quick launches and ease of storage.
Pros:
Foldable for quick storage and launches.
Collapsible if obstructed which minimises damage - cheaper in long run as the props don't get damaged easily.
They are built well and feels solid.
Looks cool.
Cons:
Less flight time - getting about 12-15 minutes as gains had to be increased.
They weighed heaps more than stock (I don't have a sensitive scale, but you can feel and see it).
Unstable at first as weight was causing the phantom to go up and down when less than 5ft. It was also wobbling a lot. Gains were then changed to 200% and she flew better but motors felt warmer.
It seems that 3 props in this size isn't beneficial as I think its washing it its own dirty air. I don't think STO did any calcs and just simply copied the pitch and length of the stock props and not factoring the number of props.
The screws for folding and holding did not work properly. If you torqued them too hard, the motors could not centrifugal balance the props. If they were loosened, it felt like the props would fall out in flight. On each flight, I would loosen the screw and softly tightened as the plastic washers would expand or shrink. So in the time that you check each screw, it would have been quicker to spin the self-tightening props on.
There was no instructions to assemble or how much torque setting was required.
Expensive - $70 inc delivery to Aus.
On a side note: You can't swap to stock to props unless you had a PC/Laptop with you to change the gain settings.
I made a big mistake over weekend. I had no access to a pc to default the gain settings. All my tilt-test footage had really bad jello when I switched back to stock props with the 200% gain settings. The 200% gain in all settings caused the camera to shake and wobble heavily.
http://youtu.be/7gJfkmXKX1A
These are great if you need to quickly launch your phantom. I've launched the phantom in less than 30 seconds (mid air checklist). Flew in ATTI mode and picked up the FPV + GPS a minute later whilst in the sky. 99% percent of the time you wouldn't need to do this.
I'll revisit this read up more about gain settings to accommodate both stock and 3 leaf. There is magic number in the gain settings that will work to improve efficiency. For now, they will be my back up props.