Lightworks is a very flexible editor. You can add custom effects and such, and really take control of different aspects of the video creation process.
The free version is nice but has several flaws. Random crashing, spotty performance, a steep learning curve...It's a powerful editor but needs to be refined a little bit more.
You're going to need to have a bit of patience when you first begin to use this software, especially if you're coming from other free video editors. THIS IS NOT another iMovie or Windows Movie Maker. This is a powerful editor like After Effects, Sony Vegas, etc. As a result, there is a technique to using this that will take time to master. But, once you do get to that point, it's a pretty nice piece of software. But, there are some bugs and the support for the free version is limited. So, make sure to keep all that in mind when diving in. But, hey, it's free so you don't have anything to lose.
Using Lightworks allows me to create videos for my work that are actually nice. It's not iMovie or Windows Movie Maker, so my presentations actually look somewhat professional.