Lessons are for wusses.
Unless you want to see your knee hanging casually around your neck, you'll NEED a snowboarding lesson. A lesson will help you build a solid repertoire of strong techniques initially. A lesson will allow you to share your frustration and successes with other starters. One of the largest benefits to taking a lesson is that you usually get to bypass all of the lift lines and get directly on the ski lift. If your friends snicker, then lie and say you got the lesson for free, so you might as well use it.