I've used it in the past to switch between two different launchers based on whether I'm at school or not. I use it to enable or disable auto rotate depending on which app I'm in. I use it to block calls from first time unknown callers. I use it to automatically silence my phone whenever I'm at school or charging overnight.
In a nutshell, it allows you to automate just about anything on your phone. You really can't talk about the power of Android apps without bringing up Tasker.
