Flex is more than meets the eye
"Creating applications that work offline is a challenge."
That will be addressed in a matter of months when Adobe release 'apollo', which allows Flex and DHTML applications to run on the desktop, with on/off line notification, an upgrade framework and more.
"proprietary Flex Data Services"
Are now provided by several non-Adobe sources, such as Red5. May even be free.
You also left out remoteing calls to ColdFusion applications, which again is free and supported by several of the non-Adobe CFML engines. Again, these may be free.
Nice comment spam above, by the way.