The Flashbender is very easy to use and immediately improves flash results and to swallow without overly much light. The Klett / pushbutton / elastic attachment is remarkably stable and damaged or smeared (unlike some competitors) flash with adhesive residues.
However, it is in principle not possible to install the Flash Bender at each flash, I have, for example, still old Metz flashes (40 MZ-II), in which there is not enough space for the rubber band because of the unusual shape. But this is likely to be a rare exception.
Conclusion: My absolute favorite flash accessory and thoroughly recommended, despite the steep price.