If you only tried your blind taste test once on one wine you should give it another try. The directions are clear that not all wines benefit from decanting. I've tried several blind taste tests and with one exception, the Venturi has always won.
Some of the variations I've tried, include using the Venturi on a $15 Cabernet vs. $70 Cabernet (the results here were mixed) when told the difference, everyone was amazed. While the $70 bottle won out in the blind test, all were surprised the other was only $15.
Also, you don't specify if you did a white wine, but I'd suspect they don't usually decant well, so I wouldn't expect them to do well with the venturi, either.
I've really enjoyed mine, but I still always taste it first with and without.