I was on a conference call with the Flex folks, in which I watched them put together a typical Shopping Cart system. The demo was very slick (as it should be) and the user experience was so nice. You could drag and drop, change views, and all of the “rich” things that you are used too on the desktop.
My only concern with some of these rich clients is the lack of a uniform UI. This has long been an issue with Flash-enabled websites. Every designer tries to do something “cool” and inheritely un-usable.
I used to study usability in a past life, and always found it amazing that even if you came up with an amazing “ne way” users still didn’t grok it like the old “ugly way”.
I wonder if there is an effort to create usability guidelines a la Apple Guidelines for these Rich applications. That would be fantastic.