There was a time when we were impatiently waiting for a Web page to load. World Wide Wait was coined as a synonym for WWW. Everything outside the direct reach of our own machines just could not be handled efficiently. But times have changed.
I am sitting in front of my Windows XP laptop in December 2007 and struggle with the exact opposite impression: It takes minutes to open Outlook, PowerPoint pauses 30 seconds to save a 10-slide presentation without a single image, and I am not sure what Acrobat is doing when starting with a PDF sitting on my harddisk. In contrast to that local latency experience all things Rich Internet App are beginning to feel fluent.
Somehow completely counter-intuitive ... And a good reason to switch fast!
Kevin Kelly states a few benefits of working with the Cloud:
1) Cloud is more reliable. Now that your entire working life and life in general is on your computer, this is important.
2) Cloud remembers to back up.
3) Cloud is available 24/7/365 from any terminal in the world.
4) Cloud can hold infinite apps, infinite storage
5) Cloud permits seamless sharing and collaboration
We add #6:
6) Cloud is faster
Background reading:
Follow Kevin Kelly's Lifestream! | Navigate with O'Reilly Radar! | Read Nick Carr's Rough Type! | Read Between the Lines!

Make sure to keep an eye on gOS!
BTW, as I am bashing Microsoft Windows, Microsoft Office and Adobe Acrobat above, pls. let me add another big player: At least on my Windows XP machine, the experience of Apple iTunes-displayed local QuickTime videos is less fluent than streamed YouTube videos.
Forrester has a report on the use of RIAs in Information Workplaces.