Oh man, now I'm two versions behind since I'm still on Win2K here at the office (system requirements) :-( Techsmith has released Camtasia Studio 6, their most excellent screencasting tool (still only for Windows). Lots of new features detailed on their site.
The most useful one for me would be the independent audio & video editing: "When recording audio and video at the same time, it's hard to be perfect. So we've made it easier to fix mistakes. Simply decouple the audio and video tracks to edit them independently. And move audio clips between (and along) tracks to line everything up perfectly. Bottom line: fewer retakes and less time spent on editing."
As always, you can download a free 30-day trial of the product. Educational pricing is also available.
Update: Lon Naylor at Screencastprofits.com has a good review of the pros and cons of this new version.