They add an Omniref “instant result” box to your Google searches.
This is pretty awesome when you kinda-sorta know the name of that one gem or method — just type it into your omnibar, and if we have something relevant, it will appear to the right of your Google results. We’ve discovered a ton of code that we didn’t even know existed because of this feature. It’s surprisingly addictive.
They annotate Ruby source listings on GitHub, so that clicking on a symbol will take you to the relevant pages on Omniref.
This is great for quickly finding information on source you view on GitHub. If you’re navigating around inside some large tree of Ruby files, clicking on a symbol will quickly get you to the documentation for that symbol (more on how we did this in a later post!)
They add the usual browser search integration: right-click context-search, etc.
Update: see the discussion on Hacker News
Update 2: We were a bit too restrictive with our domain settings, so right now the Google insertion only works with Google.com, not the international domains. A fix is pending!