For a network fileserver, resistance to failure wuld seem to be important. When I used ext2, if there was a power failure, or the machine was improperly shut down, sometimes there was filesystem corruption of one sort or another. With ext3 this was reduced, if not eliminated, and now I'm using Reiserfs, and have had no instances of filesystem corruption, of any type. I should think this is an important issue.
The OS, it's binaries and config settings can be duplicated with a little work and an install CD, but the data --That's the important stuff. It cannot be eaily duplicated, unless restored from backup. A robust, fault resistant file system should be important in your situation.
You don't indicate the intended purpose for this system, other than file service. Do you intend to offer all these files to the public? Or will there be a limited number of users? Will the list of files stored on this system grow? Will the general public be able to add new files? will the primary user interface be the user's web browser? or will users have shell access?
There is a recent thread [url http://www.linuxquestions.org/questi...hreadid=270357
Here] that has info about the apache module 'mod_userdir' that might help