I've done a number of video projects with teachers and students and I really like using Keynote to create the slides. I like how you can easily position text and graphics on a page...very easy. Then we export the slides as jpg or png files and import them into the video editing timeline.
You can also create an animation in Keynote and export that as a Quicktime movie, import it into your video editing software and preserve all the cool animations on that slide.
However, I'd recommend only doing that with one slide at a time or two or three at most. I find that, sometimes, the animations don't render out exactly how you'd like them. But one slide at a time seems to work well pretty consistently.
The only thing you have to be careful of is making sure your animation is timed correctly. Once the Quicktime export is in your video editing timeline you are limited to the length of that video clip. While some programs allow you to stretch or compress the clip, doing that will affect the clip and you may not get the kind of result you wanted. In that case you may need to go back to Keynote, adjust the timing of the animation and then re-export the slide(s).