I have a Canon HR10, and it has the option to either record in 60i or 24p. I always shoot in 24p, since i like the "slower" look and the fact that there is no "Interlace Lines" (I don't know what those are called.)
But i recently read somewhere that you always should shoot your movies with the highest frame rate possible, since you can change it to a lower frame rate in post ptroduction, and you will have more options.
I'm working on a video that's about 40 minutes long. The first 20 or so minutes was edited by someone else using Vegas Pro 8. It landed in my hands in the form of a rendered MPEG-2 file, which I brought into Final Cut Pro 5 and continued to work on. It wasn't until I exported and burned to DVD that I discovered horrible combing and/or interlacing type effects, which are only visible when played on a TV.