Q: variables with dollar sign in the flex debugger? when I debug a flex application in the properties of display objects i also see variables that start with a dollar sign, like: $alpha, $width, $x, etc..
what are they? 
are they different from the "normal" alpha, width, x properties?

A: The $ properties give access to the native player values which are hidden by the Flex framework.  The values exposed by the Flex framework can be a combination of values explicitly set or those calculated based on others or bindings or styles which are, after invalidation, propagated to the native values.  
Generally you should not refer to the $ properties unless you have a very specific reason.  
This info is available in comments in the framework source code.  I'm not sure if it's documented anywhere else.  The full mx framework source is available in your sdk directory here:
..\sdks\3.3.0\frameworks\projects\framework\src
The $height documentation says.
/*
 *  This property allows access to the Player's native implementation
 *  of the 'height' property, which can be useful since components
 *  can override 'height' and thereby hide the native implementation.
 *  Note that this "base property" is final and cannot be overridden,
 *  so you can count on it to reflect what is happening at the player level.
 */
It's marked with mx_internal so you need to declare use namespace mx_internal; to get access to it in your own class.
