Thing is, those performance issues matter. In user interfaces, they mean a lot. And they're also important when you're trying to do
actual work. I'm yet to see a web app that wouldn't choke on the amount of data a power user may need. Yes, that includes Google's office suite, which is so horribly laggy when you put more than a screenfull of content into it that the very experience justifies switching to Windows and buying Microsoft Office.
What we would need, if the browser is to become a platform for actual productivity tools and not shiny toys, is a decent persistent storage interface - one that would be controlled by users, not by applications, and that could be browsed, monitored. And most importantly, one that would be reliable. And then, on top of that, a stronger split between what's on-line and what's off-line. Because some data and some tasks should really not be done through a network.
