100% web is feasible
I've always bought into Microsoft's Software + Services story. In a nut shell, S+S says we'll get the optimal experience if we combine web services with smart software (rich clients) that can consume these services. I always used to say that some things would never be serviced just over the internet... things like spell checker and video editing would always require some fat client. But I've been proven wrong: Having a spell checker in the browser makes much more sense, and using dictionaries from the cloud can be *much* more relevant and accurate! And as for video editing... I've recently used http://www.youtube.com/editor and it has benefits of thousands of CPUs to do rendering... much better than on the desktop!
Microsoft also dreamt at one stage of "the programmable web" where even rich clients would essentially get the rendering instructions from XML, therefore making it possible to deliver everything via the web... an effort ultimately culminating in Silverlight.
But Google has been selling a 100% web vision, without a fat client. The first evidence that this vision looked promising, was Google Apps. And the proof was in the pudding that was in the form of my CR-48 Chromebook. On this machine, I have nothing but a browser, yet I have all the applications I need and want. And today, at Google IO, Angry Birds landed on Chrome. http://chrome.angrybirds.com/ Other than the fun it offers, it's proof to me of how even high-def screen manipulation and games can be delivered via the web.
I'm very excited about the ChromeOS developments, and think this will open the playing field from an OS perspective too.
Let me know what you think!