Today I noticed a small error in a graphic included in section 5.2 of the Edge RailsGuide Getting Started with Rails. I raised an issue on the Rails Github project, figuring, OK, I've made my little contribution to the March of Open Source Goodness.
I was pleasantly surprised when Rails maintainer Steve Klabnik responded moments later that I had indeed caught a bug, as he'd done a couple of days before on another issue I'd raised (does this guy never leave his keyboard?). In the earlier case, the error was on my part, a semantic mismatch between using Rails 3.2.12 with the edge docs intended for the new Rails 4.0.0.
This time, after I read Steve's speedy response, I gave the RailsGuide page a reload, thinking, "OK, it' probably be a couple of days before that change gets committed."
I was astonished to see that not only had Steve committed a fix for the error, he'd used my screen grab to fix it. Major grin :)
Coming from a waterfall-ish project world where changes can take weeks and months to find their way to end users, I'd call this delight "moving at the speed of Rails".