With over a billion users, Google’s Gmail service has been an unmitigated success since its launch on April 1, 2004. Given all that success, it’s not surprising that Google’s been reluctant to mess too much with its look. Even as Google has applied their ​“Material Design” aesthetic to a number of their apps, including Calendar, Docs, Photos, and Keep, it’s been seven years since Gmail’s last major redesign.

But that all changes this week as Google begins to roll out a major Gmail redesign. The above video provides a nice overview of the new design’s features, which are more than just cosmetic, e.g., tighter integration with Google’s own Calendar, Keep, and Tasks apps, as well as third party services. (Click here for a more detailed review of Gmail’s new design.)

Among other things, Google has brought over several interface elements from their Inbox email service. (Inbox is an attempt to provide a more experimental and stripped down email experience.) When I first tried Inbox several years ago, I really liked its streamlined aesthetic but I eventually switched back to Gmail because I missed a lot of its functionality (such as labels, which I rely heavily on to track and organize my email). The new Gmail design makes me feel like I get the best of both worlds.

That being said, the new interface is definitely busier than the last, thanks in large part to the aforementioned integration with Calendar, Keep, and Tasks. Those who are very particular about the number of emails they can see in the list view will no doubt find something to criticize, though you can change the display density to increase the number of emails that are visible. (I prefer the ​“Comfortable” option; the ​“Compact” option is too compact.)

Interestingly, the new design aesthetic isn’t totally inline with Google’s famous ​“Material Design” spec, but rather, represents some of the first appearances of an apparent ​“Material Design 2″ spec. The user interface makes heavy use of the Roboto font but strangely, Google’s Product Sans pops up here and there. And while the new Gmail’s usage of Roboto looks nice and crisp on my MacBook’s Retina display, it looks a bit blurred and even splotchy on non-Retina displays like my iMac’s.

Redesigning well-known interfaces is always a daunting challenge, especially for those interfaces used by a billion people or more. People just don’t like change, and even minor differences can be perceived as major or even detrimental deviations — even if the system in question doesn’t cost them a dime.

As a user interface designer myself, I have both respect and sympathy for the Gmail redesign team; theirs was not an easy or desirable task. Overall, though, I like the new Gmail. I’m still getting used to it, but the things that I personally care about still work just fine and even have some new features, not to mention a cleaner, more modern look to them. Which is about all I could want or ask for.