Acutally, it isn't. If you know how to set it up and how to fully use it, it's a VERY, VERY good operating system.
Like I've always said, Windows isn't for everyone. Neither is Linux or OS X. It depends on your preference and usage. So boldly claiming that "Linux is useless" is false to a certain extent. It might be useless for you, because you don't know how to use it, but there are a lot of people out there who would beg to differ.