Though the gameplay looks good, what we can't so heartily endorse is the video's dialogue. "Now, you may be asking yourself: 'What exactly is a MOBA?'" Really, guys? That's the "A" material?
[Update: Andrew reminds us of a very important fact we neglected to mention: League of Legends will be totally free to play. In fact, you'll only be spending cash if you want to customize the look of your character.]