Mac software for developing a product video I'm looking to develop a video for a software application that I make. I'm willing to spend a lot of time learning the software, so features are more important than simplicity.

I've got access to the full Adobe CS5 Suite, however I don't think anything in there suites my needs: Premiere Pro and After Effects seem more orientated to video shot with a camera than screenshots, adding text, etc. But I may be wrong.

What I want is a professional video with good voiceovers, slick movement, screenshots and some demonstrations of the product. Some effects will be required - It should look professional, not like something done in Movie Maker.

Any ideas? Multiple pieces of software used together is fine (I'm sure CS5 will come in useful in some regards).
You want ScreenFlow. The website isn't all that well designed, but ScreenFlow itself is a very nice and nice-looking Mac app. 

Depending on how fancy you want to get with transitions and effects, you might find it useful to export clips from ScreenFlow and composite them in something else. But there are plenty of product demo videos for popular Mac apps that  were done completely in ScreenFlow (examples elude me; help, commenters?).