Decanter did another trial of this kind within the past year or so. It was pretty interesting, but not particularly conclusive. I think the general conclusion was that decanting doesn’t hurt, but may not help.
Having said that, I tend to subscribe to the thoughts on this written by Prof. Waterhouse of UC Davis, which can be found in this article:
http://www.curiouscook.com/site/2009/01/for-a-tastier-wine-the-next-trick-involves-.html
Mr. Waterhouse thought the elimination of sulfur aromas is all that these accessories — or, for that matter, aeration — had to offer.
“A number of sulfur compounds are present in wine in traces and have an impact on flavor because they’re very potent,” he said. “Some are unpleasant and some contribute to a wine’s complexity. You can certainly dispose of these in five minutes with a little oxygen and a small area of metal catalyst to speed the reactions up, and change your impression of the wine.”
But Mr. Waterhouse maintained that no brief treatment could convert the tannins to less astringent, softer forms, not even an hour in a decanter.
“You can saturate a wine with oxygen by sloshing it into a decanter, but then the oxygen just sits there,” he said. “It reacts very slowly. To change the tannins perceptibly in an hour, you would have to hit the wine with pure oxygen, high pressure and temperature, and powdered iron with a huge catalytic surface area.”
So why do people think decanting softens a wine’s astringency?
“I think that this impression of softening comes from the loss of the unpleasant sulfur compounds, which reduces our overall perception of harshness,” Mr. Waterhouse said.
For me, there is zero question that aerating a wine (particularly a young one) is beneficial.