[edited to be more like a question.]
I have been producing video using a combination of ffmpeg, mencoder and graphicsmagick for several years. Mostly it is because of not only the sorry state of affairs of GUI editing tools on linux, but also since I prefer to use the command line and scripts more than clumsy crashy interfaces.
I investigated the MELT CLI after stumbling across a couple of youtube videos showing how it works.
As opposed to ffmpeg, it is FRAME-PERFECT, allows for simple concatenation of files or even clips within multiple files, transitions are incredibly easy and the usage of video and sound filters is intuitive (once you have wrapped your head around the syntax). In fact, you can even script effects with html5!
Here is an example that would provide both an audio and video transition between clip1 and clip2 and create an mp4.
$ melt clip1.dv clip2.dv -mix 25 -mixer luma -mixer mix:-1 \ -consumer avformat:clip1and2_mixed.mp4
From their webpage regarding their system / plugins:
FFmpeg for audio/video decoding and encoding swfdec Flash decoder WebVfx for HTML5-based graphics/animation generation GTK+ and Qt for image loading and text rendering LADSPA audio plugins SoX audio effects libsamplerate audio resampler JACK audio routing frei0r video plugins SDL for desktop audio/video output
Note: I am not knocking ffmpeg and I am not affiliated with MLT or MELT.