To me web app replacements of desktop apps sometimes feel like a camping trip. You can survive just fine, but not comfortably. Esp if your app needs to talk to the GPU, iPhone or other devices...
That said invisible updates and implicit backups are great.
Imagine a world 10 years from now where everyone bought a fully enclosed computer like you would buy an iPhone now, but you have to pay a monthly subscription service to get updates or to use it. That's why all these companies are making web-os, thinking that's the way of the future. It's going to be horrible.
Seriously, as much as I like open source software (and I really like it), I can't agree with you on this. I think you're doing raymondism.
There is little innovation in the open source world; it's mostly about making better implementations of things invented long ago by companies or universities. But that's OK because in the end we get good software.
Of course it would be neat if they could sell you bursts of processing power from huge servers somewhere. That would be an improvement over desktop versions.