Today is the day, 21 April, the algorithm has been rolled out. Expect to see some of the good and bad news about the update soon.
This change is different and much welcomed. Yes, many people want this as it is for the betterment of conversions for website owners. Also, since this is not a penalty, one can easily work up if they see a dip in rankings.
The comeback will be easier when compared with Panda and Penguin update. Understand your customers better now.
Mobile Friendly Update
Yes, that is what Google calls it. Don't stress if you have been not able to meet deadline of today and some of your webpage's are not friendly. You can still work on it. This update takes changes in real time.
What does this mean to you?
You can make a big change in your site today, and expect Google to pick it up soon. Google is analyzing the site on a page by page basis. This means all of your sites pages has to be mobile friendly.
Many of the bloggers and site owners have adapted responsive design, you may however choose to have a separate mobile website.
Boost In Rankings
As Google has stated, this algorithm will affect more than previous Panda and Penguin algorithm. But, this is only for mobile search results. This means if your visitors are coming from mobile, than you can expect a change in rankings.
However your desktop site rankings would remain the same.
Google will keep on updating the algorithm and keep on bringing new updates, as long as you are following steps for increased user benefit, you would be in alignment.
Act now, if still your site is not mobile friendly.