He talks about improving the development workflow by hot reloading parts of the application during runtime. Slow workflows affect every developer and the idea from this talk can be used to build tools for other stacks or languages.
I'm not sure if I would define it as a "talk" (and the details are more meaningful if you know how to use Emacs), but Jay Dixit explains how he uses Emacs for writing instead of programming: https://www.youtube.com/watch?v=FtieBc3KptU
As a rails dev this one is probably pretty standard but I appreciated DHH's ideas about being small and still able to take on the giants.
https://www.youtube.com/watch?v=KJVTM7mE1Cc
