Long-time (10 years) user of Apollo Bio-Fin Pro, with spring strap. Wore out one set of spring straps, but the fins are doing fine.
There are pros and cons for these fins. They are natural rubber split fins. They are very efficient. I swapped fins once with a buddy, and it was like wearing nothing at all! I thrashed my feet, but didn't seem to move much. Meanwhile my buddy would flip one fin and be 10 feet ahead. Bottom line is, they work very well indeed for moving forward and saving air.
The con is that they are heavy. Heavy to pack, and heavy in the water, so they tend to pull your feet down. I sometimes blow air through my wetsuit into my boots to help trim them out a bit.
Being soft, they also are not easy to back up in. You can do it, but slowly. I assume a stiffer fin is better at this.