I like how easy it is to learn how to use Screenflow. It didn't take me long to accomplish the handful of tasks I was looking to accomplish. You can also set templates for things you reuse on a regular basis, which makes video editing faster. I also love that you can export your work as an animated gif, which is often a better method of displaying it to the end user.
They have just enough features to put together professional looking videos, but not SO many that you get overwhelmed. I wouldn't recommend it for 2-hour long, feature-length, cinematic movies for the big screen... but that's not what it was designed for.
For creating educational videos, it's the perfect blend of professional features with ease-of-use.
It's also very affordable, and they host frequent webinars, as well as post many video tutorials on their site. These are wonderfully done and really help learn the new features... and some existing ones you didn't know existed. Review collected by and hosted on G2.com.