Good point. I think user experience is important as well. But as demonstrated by many of arcane JavaScript emulators out there (vi, terminals, etc), I'm sure you could devise just about any user experience you would like in a simple web page. I'm not sure the Windows and Mac OS killer exists yet, but I think they will become increasingly irrelevant (as well as the non-browser apps installed on them).
And you seem to forget, unless I'm misreading you: a part of using an application is the experience it provides. What are you saying will beat Mac OS and Windows? Google Docs? Buzzword? Hardly.