No.-using brand-names tends to limit the appeal of your story to a particular region and time. its also usually a lazy way to write. for example, instead of saying a character is rich, you might say he shops at dkny rather than walmart, but it is more powerful to describe the clothing itself rather than relying on a brandname. for example, someone replaces his clothes every season to be current is wealthy. in contrast, someone that wears his shoes until the soles burn out is demonstrably poor. in contrast, by using a brand-name, youre betting that the vast majority of your readers will know what youre referring to. even if thats true now, will it be true in 10 or 20 years?