Just to clarify...
While you DO need final cut pro to import/edit/export native 24p footage, all is not lost with final cut express.
I just finished up a project that had a few different formats (24p,30p,etc...). Final Cut Express 3.5 imported and edited the footage flawlessly. Now we ended up just exporting for the web (and it looks awesome).
However, *I've heard* where final cut express 3.5 falls short is its ability to preserve 24p. aka if you need to have the 24p preserved throughout your workflow and then say.. printed to film.
Now, I'm no Final Cut expert, but just wanted to say that if your end goal is just getting the footage imported and edited (and in my case..exported), Final Cut Express 3.5 should work just fine for you. I did not try importing the footage into iMovie.
Finally, if you need to move to Final Cut.. I recommend express if $$$ is a concern. I believe it can be found (legally) for sale around $150. Not a bad deal for what you get.