The hype also doesn't take the negative research into account. Contrary to Dr. Nissen's portrayal, a number of studies have found no significant changes in strength, body composition, markers of muscle damage or sports performance with HMB supplementation. Looking closely at these studies reveals an interesting difference, however. The positive studies used either untrained subjects or subjects with varied training experience. In contrast, the negative studies used highly trained athletes.
Perhaps this explains the disparity in results. For example, it's possible that a) experienced athletes need a larger dose; b) need to take it longer to see results; or c) both.
In my opinion, however, another, and more likely, possibility, is that HMB provides a small, but significant boost for people who are just starting to work out. It's a different story for people who are adapted to training.
"Real world" experience seems to bear this out. Very few experienced bodybuilders have reported any benefits from HMB supplementation. I certainly didn't notice any when I tried it, nor did anyone in my immediate circle.