You could use mx code to build RIAs with learning none or
minimal AS3.0. However it seems to be, and correct me if I am wrong
anyone, that developers like to use mx code to layout their
applications interface and not necessarily have it doing logical
computations as that would be done by AS3.0 code.
And the switch to AS3 is not that difficult. Tougher data
typing, no more "undefined" on everything, stuff like that makes
migrating an app a bit of a pain, but syntactically the differences