This stuff has some possibilities so far. However, vanadly, like creatine and most other supplements are way over rated. They do not work miracles. In the case of VS, there are more than ample ( and recent) studies that do suggest there may be some ergogenic effects gained from using this one.
VS has well-documented insulin-mimetic activity in NIDD and experimental models of diabetes (Brichard et al. 1995; Cam et al. 1995). So this effect in itself could be useful in human protein synthesis stimulation. In fact, many bodybuilders still continue to report the anabolic benefits VS even though this stuff has been on the shelves for a few years now. I think Dave will agree that when a supplement doesn't work, it soon quits selling. I'll be willing to bet that VS still sells pretty well too.
Now there is an interesting 12 week study by Fawcett et al. (1996) that found that VS did not significantly (note they said significant) change body composition after a DEXA scan, though the group did show some body weight gains. The gains were greatest in the group that used VS during the first 4 weeks, after that both groups gained almost the same. Also during the first 4 weeks the VS group showed small increases in blood glucose and insulin levels.
This study also measured performance using the knee extension. They concluded that VS somehow accelerates performance improvements produced by training. No explanations on how thought. Apparently there is a need for further research in the aspect of VS supplementation.
Two of the subjects did report tiredness, fatigue, mood changes, and anger during the first 6 wks and had to drop out. So the researchers advise that athletes should carefully weigh the possible benefits against potential risks. They also suggested possible modest ergogenic benefits occur ONLY within the first 4 weeks after that....zilch. So this might be a wise time to cycle off the stuff after 4 weeks. Much as the anecdotal recommendations of bodybuilders have suggested in the past.
While VS shows some promise it is still much the same as creatine or protein supplements....don't expect magic. It still takes lots of hard work in the gym.