Advertising and marketing are not forms of propaganda, they are simply forms of free speech. Just like anyone else, ads can say what they want to within the law. They can't mislead anyone, but consumers should do their research thoroughly before buying any products or engaging in any consumer activity based upon commercials alone. There are plenty of sources online to research new products to see what other people have said regarding certain consumer items.
Marketing and advertising are essential to a business to stay alive. It is not likely that many business will use biased information to promote their product or service. This is because of the information behind the product will spread through the internet, usually on product reviews and rating sites. They cannot just straight out lie to people on their product working when the actuality is opposing. That is called "false advertising" and it can go to unneeded lengths at times. Businesses have to be real careful, because, reputation and your business's image is not something you want to ever mess up. So in all, it can be a little over exaggerated, but that usually what business is, trying to make it sound like it is the best, but it wouldn't be something that is generally misleading or biased.