It will be nice if every user can have access to their directory. When using wordpress as a CMS it will be really usefull.
Eg: User1 have to upload a video, so he will upload it to ../user1/file.mpg
And it will be more usefull if in the admin panel, every user can create subfolder. So if the user1 want to put a video in /videos/file.mpg he upload it there. So, if he's using a plugin like podpress he won't have to go to the FTP client (it will be more secure if we are not giving the FTP to a thousand users :s). He will upload the video, store it at his directory and just put the url directory.