This actually isn't a bug. Buttons in Flex and Catalust don't change the cursor to the hand by default like Flash. There currently is a way to control the cursor in Catalyst, but is something we will work on in a future version.
you can easily add this in Flash Builder by adding the code below to your button (or other component) :
In the next public beta of Catalyst you should be able to get the hand cursor without editing the code. Completely custom cursors is something we are looking at for a later, future release.