It's been useful for me. Back in high school, I raced to 50 problems against a friend and learned a lot along the way. Sure, you can get problems elsewhere, but

It's been useful for me. Back in high school, I raced to 50 problems against a friend and learned a lot along the way. Sure, you can get problems elsewhere, but the site has a nice way of continuously upping the complexity to enable self-learning.