The check-in feature is the unsung hero of the updates. It won't be the most-used feature they add, but it's a very smart addition. It leverages the privacy controls they've developed over the last several years, along with location-based automation, to provide a basic service that people do every day. The benefit, though, is that it will let people know if something's gone sideways. Because it can be set up beforehand and remain discreet, I imagine there will be a lot of women who welcome the feature, and I'm certain it will, at some point, save lives.
The other stuff is neat and some nice changes, but I really do think check-in could quietly become a key feature that draws some people to the app.