Openshot, an open source non-linear video editor, has received a lot of positive reviews especially for its simple and user-friendly interface. There is no official Gentoo ebuild for Openshot but I have been installing and testing the luman overlay (Openshot 1.4.3) over the last two days which seems to work fine.
Together, Linux NLE video editors provide a very powerful capability although each one tends to have unique features meaning it's sometimes necessary to use more than one piece of software to achieve a desired end. Cinelerra is particularly powerful and flexible, but I spotted recently that it can't generate a wipe transition with a softened edge (as noted in this rather dated review). This led me back to Kdenlive (an excellent program in its own right) and then Openshot for this feature. Initial impressions of Openshot are that it is similar to Kdenlive but with the ability to generate 3d titling through a simple-to-use interface to Blender. Note that the luman overlay does not install Blender, you have to install it separately and it has to be a very recent version. At the time of writing this is Blender 2.63 in Portage (Openshot requires 2.62 or later). Blender looks very complex to use (I am not familiar with it) but the Openshot interface to Blender is straightforward, offering a range of effects such as dissolving or exploding text and a few parameters to adjust for each effect (such as the colour of the text). The rendering of these effects is very processor-intensive, I gave up waiting on a single-core machine and ssh'd to a triple-core machine on my home network. The time waiting for Openshot to render is a reminder that Cinelerra's render farm is a great feature.