I have tested the Vinturi and it does work immediatley, both on the nose and on the palate. However, I do not own one. I either decant for all the reasons Peter listed, or I pour into wine glasses and let them air, as David indicated, taking a sip once in awhile to witness the wine evolve (I usually do this while preparing dinner). To take the guess work out of the decision, I decant practically every red wine I open with one guideline: older wines may need less time to fully open up and, if left to long, may degrade before you know it.
Unlike Peter, I always place the wine bottle on the table next to the decanter no matter how unattractive it may look.