New features include:

Macromedia Generator Developer Edition
Movie Explorer
Smart Clips
Macromedia Freehand Import
Bezier pen tools
Shared Symbol Libraries
Web-native printing
QuickTime & RealPlayer support
ActionScript development tools
XML transfer and HTML text support

You can get it from: 

<http://www.macromedia.com/software/flash/>
(there is also a 30 day trial version available)

More info, and screenshots, at:
http://www.macromedia.com/software/flash/productinfo/features/

Of particular relevance to this list is the inclusion of ActionScript
development tools, featuring a debugger and editor, amongst other things.

I think one of the most interesting additions in v5, IMHO, is the matching
of the ActionScript syntax with that of Javascript!

What do you think? 

Regards

Jeremy Walker
(list moderator)