I took a number of Philosophy/Logic classes at University. I found them both interesting and useful. I think I learned to be a more reflective thinker, not to jump at the first idea presented in a debate or discussion. It also taught me to seek evidence rather than opinion and that research had to be an act of discovery rather than an act of confirmation.
I learned a lot about political and historical Philosophy, some of witch helps us to make sense of the word...I guess.
Perhaps there really is no such thing as useless knowledge.