From my experience, yes it works.
It needs to be used in conjunction with the usual basics, stretching, correcting posture, increasing flexibility, etc, which address the underlying cause of injury. The NO patch provides the actual healing of the tendon.
Dr. Smith, the remark about superficial tendons is spot on. I am already convinced that it works on my elbow and knee. Other potential hotspots would include: achilles tendon, wrists, and possibly the suprispinatus and hip. The first I heard of this was actually from someone treating their hip with the patches.
The reason for developing tendinopathies all over the place stems from being an overly ambitious engineering student. I was doing too much and sleeping too little. I was also on the crew team and doing two-a-days, not warming up properly, not eating/supplementing properly, etc, etc., you get the idea. Anyways you live and learn that warm tendons stretch and cold ones are irritable, and that recovery is King.
One more thing about the NO patches that gives you an idea of just how underdeveloped the treatment is: The patches are actually intended for angina patients, basically people who have clogged hearts and need the help of NO to open up blood vessels. So these are readily available at your local pharmacist, and you basically cut them up into quarters to lower the dosage. IMO neither the dosage nor the application (topical cream may work better?) has been optimized. The thing is that you do need a prescription.