According to what I've seen from Google so far this will be a much harder impact than both the Panda & Penguin.

I'm already getting messages from HostGator wanting me to purchase some "get mobile friendly" products they've come up with.

Most of my sites are WordPress, and easily made mobile friendly with plugins.

For anyone who isn't sure about the mobile friendliness of their sites here's the URL of Google's mobile friendly tester page:

https://www.google.com/webmasters/to...obile-friendly

Just plug in your domain.