Principles of Rich Web Applications
I think these are great ideals to strive for, but they seem lower priority than a couple things that they can get in the way of if you're not careful.First, in your quest to show me the latest info, please please please don't introduce race conditions into my interface.  I don't want to go to hit a button or a key or type a command, and have what that means change as I'm trying to do it.Second, it's often important to me what has happened locally vs. what is reflected on the server (especially if that's public).  Please do update the interface optimistically in response to my actions rather 
than sitting and spinning, but please also give me some indication of when my action is complete.