I just downloaded the 30-day trial of Camtasia for Mac and am quite excited! Of course, most people think of Camtasia as a screen-capture tool for creating tutorials and such, which it does very well in this version, too. (It only captures full-screen, but it is very easy to crop to the selection you want later.) Here is a chart of the comparisons between this first version of Camtasia for Mac 1.0 and the Camtasia Studio for Windows 6.x product.
Only having spent a little time with it, my first impression is that, as well as an easy tool to create tutorials and screen captures (including video and sounds), Camtasia for Mac is a fairly full-featured video editing program that is also quite intuitive! You can import images and layer videos on top of them, layer videos on top of videos, easily separate audio and video lines, apply effects such as one similar to the Ken Burn's effect to videos after the fact, and much more!
The share menu item allows you to share to Screencast, YouTube, or iTunes, and the advanced export function allows exporting to AVI, QT, MPEG-4, and more, with the ability to pick your codec and quality options.
The TechSmith Web site has a great set of tutorials located here if you want to get a feel for the options it offers.
I might have found an easy-to-use tool that allows me to both create tutorials and access to a simple, but effective, video editing program! If you try it out, leave me a comment and let me know what you think!