I'm getting the 8g and estimating about 700mb for system software, my breakdown of space will be:
- 5 GB Music
- 1 GB Video
- 500 MB Pictures and Address, etc.
Give or take a little space, that will leave me close to a GB for email, attachments, etc. I can fit about 3 movies in a GB and I don't see much reason for more than that at any one time.