Let's look at what Google has done. Probably the most original thing in Chrome is that there are tabs where the title bar used to be. The person who can script them out and make them accessible through libwnck or some similar desktop environment based API will certainly get alot of kudos from me. Really, the concept does not belong to Google, but I believe the credit should go to Opera for first integrating the browser widgets with the tab. Another revolutionary concept is binding processes to either tabs or sites, or other process splitting criteria. Again, the credit goes elsewhere, to Microsoft, but thoroughness that Chrome uses is pretty remarkable. In fact many of the 'unique features' in Chrome have already been implemented elsewhere, in some fashion.
Chrome isn't an OS though. If it was, where is the Desktop Environment? Where is the kernel to run it all? Where is the hardware support? Where are the millions of man hours that go into releasing a top notch operating system? Too busy writing browsers apparently. Chrome is no more an OS than .Net or Python are OSes either. Chrome is a virtual machine / application container. Way back when, in 1995, there was a question on how to run code both on a client machine and a more powerful server. Way back in 1985 the same question existed. There are rather large sections of Tannenbaum's Principles of a Modern Operating system that go into RPC functions and function stubs. For those of you with long memories, you should all remember how Java was supposed to revolutionize the web, by making it more 'desktop application-like'. As a developer of web applications, i always struggle with the concept of how my code runs like a weird application in the server space, but just a bunch of documents in the client space. I really would like to see more tools that unify the design a bit more, and many of those kinds of tools are coming of age.
Google has been at the forefront of these design paradigms, with Google Gears as their showpiece. Having little personal experience with Google Gears itself, i can't really comment on how it works with Chrome. Just realizing though, how cleverly Google has wrapped an essentially document oriented display framework with a sophisticated programming language on top into a virtual machine system that can interact with the user's desktop in one smooth paradigm, and I can't call it anything but a Virtual Machine.