That's why they've had the Mobile option in the Page Speed Insights tool for a while now. They're pretty good about hinting which directions they're heading in for the most part.
Which is why I've been testing sites that I build with mobile devices for a few years now, and why RWD & other device consideration is a standard part of my design flow from the start, even when a client doesn't understand it at first.
It's all about that mito tag site speed bro...
This one was fairly obvious move actually. In fact, I think it's more important for your site speed to be as fast as possible with mobile, since people/mobile providers (Look at you AT&T) still have shitty slow connections. It'll teach people to use less clunky code and "reduce to a minimum all that is un-necessary."
Indeed - here in the UK people that I know adopted mobile internet a long time ago when networks were slow and displays tiny. Now nearly everyone (apart from the more remote users) have fast internet connections on their mobile devices, and are increasingly using them as one their main portals to the web. This figure is just increasing all the time and speed is critical not just to SERP results but to overall effectiveness.
It really won't be long before you notice a new breed of sites popping up that make intelligent use of a combination of geo data (true* local search), device profile modelling, user data from inter-site connections and more...
This, my friends, is the way forward and how we can really target a prospect with exactly what they "want",
can afford, and are likely to buy.
I shall not use this opportunity to spread my evil word of Mobile SEO or I shall get shot down in flames by the disbelievers here** apart from to say I don't think it will be too long before 'mobile device' web access is more commonplace than desktop. Also - I honestly don't know if any of you are building these sites yourselves already, in which case I'm just saying stuff you already know, but you might want to start thinking about flexible displays how to design for those soon.
I might sound like a pompous stuck up twat, but trust me on this: Mobile devices are the now and
the future.
*the surrounding hundred yards of the user in metropolitan areas.
**plus I'm really learning a lot about AM from you chaps (which I find fascinating) and don't want to appear like a snob - I'm eternally grateful!