"Letting the wine breathe" has become a joke, one of the pretensions that make wine drinkers so comical and intolerable to the rest of the population. But it really is a good idea, and not just for expensive bottles. We've found that inexpensive reds benefit enormously from a breath of fresh air.
A wine that can taste sharp or flat straight out of the bottle often deepens in delicious ways when it's given a chance to open up in a glass or decanter. So, if you know you're going to be drinking a certain bottle with your pasta, crack it early and pour a couple of glasses before you sit down to dinner. You'll be pleasantly surprised.
On a related note, we've been seeing ads for the Rabbit Aerator, which allegedly performs the same function for $30. We asked one of the knowledgeable wine guys at our local liquor store about this device, and he was unimpressed. For the same price, a decanter does an indisputably fine job. Or you can just plan ahead and open your bottle ahead of time, for free.