Well, what a coincidence, that friend is just busy setting up a dspace server.

It depends mostly on what programming language and database you want to use:
Eprint: Perl with Mysql
Dspace: Java with Postgress or Oracle
Fedora: Java with Almost all databases

One disadvantage of dspace is the way the files are saved. The pdf's are saved 3 to 4 layers deep, and get a number as name.
The database gets quite complex too, because everything is linked to everything else with 'unique identifiers'

Hey, you'd think i knew what i was talking about here, just relaying / translating though