This is pretty cool. I use GIFs for marketing for my SaaS startup[1] because it has the best support for autoplaying across devices, but the file sizes are a bit high (690 KB and 270KB for screencasts of a few minutes each). I use licecap[2] for recording and Gifsicle for optimizing, but perhaps I should give ffmpeg a go and compare the results.

[1] https://zapla.co

[2] http://www.cockos.com/licecap/