Every trip out to Google for something we do not know costs 10 minutes. If our search returns visited links then that was 10 minutes needlessly wasted.
It's important that I write what I didn't know with pen and paper because I type for a living. There is something about seeing that information in a second context that etches it into my brain. So much so that the mere act of writing the syntax down immediately before using it is often enough to induce memorization without the need to review the information later. Waiting until I need that information a second time (looking for the purple links) before committing it to paper provides a great filter so that I'm not committing obscure 1-time-use trivia to memory.
I now produce at double the speed that I used to because I'm not constantly shifting focus between my work and a browser. I also find that I'm more creative. Since I now speak fluent Ruby I can use lateral thinking to compose thoughts outside of a phrasebook. The speed is wonderful but that increased creativity means that I'm more likely to build stuff that somebody might actually use.
That seems like a pretty nifty metric, right? Building a thing that is used by humans.