Do you remember the days when your mom used to "rake" the carpet? Only the rich people had shag? Green? Orange? Multi color? I once went on a listing appointment for a house built in 1960 that had black shag carpet in the bathroom! The owner said he had heard it was coming back in style. No! Never! Not black shag! and definitely not in the bathroom.
One question I do get asked alot is do I need to replace my carpet to sell my house. That depends! Most of today's buyers do prefer hardwood floors, especially in the main living areas. If your carpet is over hardwoods, definitely up the carpet and refinish the floors. If you can afford to add hardwoods at least the the main living area, that would be great. At minimum clean the carpets professionally to remove any odors or stains. And PLEASE, no carpet in the bathrooms!