{} brackets used for data binding (pretty basic)
Using typing in AS3 improves performance – so use it
Create custom classes like:

package com.ted
{
import mx.controls.button;
public class MyButton extends Button
{
...
}
}
// then use like:
<ted:MyButton label="..." />


Flex compiler has a -keep property that will dump all generated .as files for inspection
Flash 8 SWFs can talk to Flash 9 via LocalConnection (otherwise they are sandboxed)
Flash-Flex connector kit lets you export MC as Flex Component for use as <mx:… />
Scale9.com has theme packs for flex; crack one open to see how its built.