All three of those you mentioned provide good functionality depending
on what you are looking for. How hard to install and manage depends
to a large extent on your available expertise. In the case of DSpace,
the one with perhaps the largest installed base, it's not unreasonable
to have it up and running in a few days if you know something about
systems. I managed to have a functional system running in the Amazon
cloud within a total of about 8 hours and with no prior knowledge of
the system. That included building the system from source and doing
some minor customization. However there are easier approaches. For
example, if you are willing to pay just a little more you can get a
preconfigured AMI that enables you to just create a virtual machine in
Amazon's EC2 and then run it. That said, you'll still have to learn
how to customize it. I would recommend investing the time to
understand it yourself, even if you contract with someone to help you
get started.
All three systems have good user support groups and forums. As I
looked at them it seems that while Fedora has the most raw
functionality, it does not have as much of the user experience ready
for you out of the box and seems to be more difficult to get going
with from scratch. EPrints is easy enough to get running, but seems
more limiting in terms of functionality. However these evaluations
were quick and somewhat superficial so I will quickly yield to others
who might have more detailed analyses. That said, you can find
comparisons or evaluations online for these different systems.
Other systems are coming along. Archivematica looks promising, but is
not yet ready for prime time. Perhaps it will be in the next six to
twelve months, but I think there are some inherent limitations that
need to be addressed. Nothing that can't be addressed, just that
haven't been.
Good luck in your search. Don't be afraid to try DSpace. It has lots
of information online. Some of it is a bit inconsistent, but it is
possible to work through it.
tc