One thing noticeable right off the bat is the new parental controls tab in the Preferences. You can now disable podcasts, explicit material, the music store, and shared content. 5.0 also offers calendar and contact synchronization if you are using Microsoft Outlook or Outlook Express.
Unfortunately, I don’t use either, so these last two things don’t help me a bit. As far as the music store goes, it still feels dog slow to me.