There's been some more mystery meat features slipping in there too somewhat unannounced; if you click a committer icon a little filter panel opens on top that lets you see how many commits in the view were by whom, and if you click one of those, hide those commits. I got the idea when I was playing with Autopatchwork at some point, unpaginating a whole repository's worth of commits and wanted to slice and dice the view a bit, get aggregate stats and the like. This is what Greasemonkey's early history (from 0.8 and back) looks like, in terms of authors (not committers) involved, for example:
Autopatchwork could use some more coverage on the English-speaking web, by the way, because of its neat way of aggregating user data from contributors. Instead of a dedicated backend server someone maintains for the script to work, it's using a wiki-like JSON database for public domain content: Wedata.net; define your json schema and let anyone that wants to fill in, edit and co-maintain the data (here: unpagination url regexps and node xpaths). The editing process looks a bit like this. I am especially glad to have found it, as I've been wanting a service like that for a long time but not really wanted to host it, and having a public cloud sync point for mini-applications like this to update their localStorage copies of the data from is a neat trick.
Anyway, happy githubbing! As with so many little features before it, I already can't fathom going back to a github without this feature (and I've only been using it since yesternight). It helps a lot seeing what went into which release at a glance, without doing all sorts of manual work. It would be nice for it to mark branch-off points too, but it would require some kind of merge-base type api end-point, for digging up where a branch's closest common ancestor is to all other branches. Maybe time for devising a neat response format and crafting a little api feature request.