I went over some of the highlights of the my initial product review of the AutoCAD 2009 release in this article back in February.
In April, AUGI HotNews published my TipNiques column on the Interface changes with ACAD09.
And in May, I did a follow up (AutoCAD 2009: Odds and Ends) listing all of the little changes, enhancements and new features that I'd come across.
In June, Brian Benton is scheduled to round out this series with a good walk through on the Action Recorder, so be sure to check it out.
There have also been some articles in AUGIWorld and in other HotNews columns about making the most of new features.
And, please note, if you want the menu bar back and things to look more traditional, just switch to the Classic Workspace.
Of course, if you're not quite ready and willing to upgrade, feel free to refresh yourself and make sure you're taking advantage of the AutoCAD 2008 features!
TIPniques: Dashboard Customization
TIPniques: Using Referenced Files
TIPniques: AutoCAD 2008 Odds and Ends