Huh - I am very happy with mine - it has saved the tendonitis from neing inflamed by shaking paints, and only by holding brushes...
I have found, however, that I need to take one day every 2-3 months, and expect to spend 4-5 hours doing other things with that incessant rattle going on as I run every single paint through for 10 minutes or more.
And while the strap broke the first time in a month or so, the actual shaker lasted almost 6 years before I had to replace it.