The open source GaleForce project lets you root Google Wifi

Depends what you want to do. Getting root access opens things up. Getting root was possible on onHub last year and another wonderful gentleman from the onHub sub was able to get onHub running as a speaker of sorts, but as of additional functionality as a Wi-Fi router, it has yet to be done.

It isn't that it can't, perhaps the community has other things to do, but this does/can open up it's future to DD-WRT/Tomato/etc. Again, onHub was rootable more than a year ago.

As deztructo says, it depends. Personally I've only put it on the main device. I actually like the simplicity of the device/app, despite doing this. I like having it on the main device (with minimal changes), so I can fix the sort of niggles you see here on this sub-reddit (or the official Google Wifi product forum), while also keeping the automatic security updates, east of use, and so forth that Google provide.

It is really easy, but beware my if you hit obstacles there is nearly no support. I don't think the dev that wrote Galeforce is even supporting it any longer. There's a growing list of open issues on the GitHub repo.