I'm still living the Google Drive world with its docs and ALL file format compatibility. I'm checking my google mail on my PC and my phone.And getting notifications wherever I am. I can check what my friends are doing and chat with them. By that I mean give my 5 word comments on twitter or in a growing thread in their blogs.
So do I need one operating system to rule my devices. Certainly not. I can do a lot with a smartphone and its apps.
Ubuntu's proposition is that a single user experience is the goal. To achieve the goal, the way is one operating system to rule the desktop, laptop, tablet and phone. After Microsoft's domination of personal computing, the suggestion of one OS sitting on all platform is going to be met with doubts even with an open source OS.
As a desktop user and smartphone user, I can believe in the vision of enhancing the user experience. I mean why dock a phone or use a usb when you can just jump from phone to desktop and vice versa.