For really good quality XVID/DIVX type video, you're looking at approximately 350MB per hour. Most people rip so you can put one movie or two 1hr TV shows on a CDR.

That's about 80-90 hrs for 30GB. It varies a lot though. On the screen of the Archos, you could probably cut the size in half and not notice the quality difference.

With the Archos, they might be talking about the number of hours of video it can record. Don't know if they assume you are using the "best quality" setting on the player.

I think Itunes only works with Ipods, but I haven't tried it, so I can't be sure.