Chrome OS is a nice step from Google to give users a pure Google experience on desktops. The Google Apps that most of us use in daily life are well-integrated in Chrome OS. One of the good thing about Chrome OS is that you can install it on most of the hardware. Here's a guide for those who want to try Chrome OS.
Chrome OS is an OS in which you can't do anything without Internet connection, because most of the apps need Internet connection to work. You can use the Extensions from Chrome Web Store as native apps in Chrome OS. The overall experience you get on Chrome OS is fine but still needs improvements.
I used Chrome OS for almost a day and I didn't like anything except the interface. I was browsing Behance and found this amazing Google OS concept.
We have also seen the use of full screen interface on Windows 9 concept. The login screen is Mac like lock screen with Google profile picture. The Start screen is much like Chrome OS's main screen, the only difference is the Task menu is at the top and widgets. The Start screen displays a time and weather widget, and you can add more widgets.
The users can access File & Folders by swiping from left and Hangouts app by swiping from right. The Task menu includes the App launcher and pinned apps. I really like the flat interface of Google Chrome and Gmail. Gmail design is minimal and clutter free.