The learning curve depends on how much time you want to spend learning the GUI and (most importantly) WHAT TO DO in case of a drive failure, how to recover, etc, etc. They key to any kind of raid or NAS setup is what to do in failure scenarios and how to do it. Practice some before comitting to the use of a NAS and remember, using a NAS does NOT reduce the need for backups. It just makes the eventual use of those backups somewhat more distant.
Remember no one cares about 'under the covers' as long as all the lights are green and data flows as required. Its' when the lights turn yellow and red that the skill of the integrator (human) and the recovery options in the software that makes all the difference in the world.
And it's not just for home hackers anymore (and not since 2002).
http://www.tomshardware.com/2003/04/25/hard_drives_instead_of_tapes/index.htmlThe thing is linux under the covers, but there is a pretty nice GUI wrapped around the software. Their on-line support forums are pretty helpful as is the documentation. AFIK there is no trial download available which is a pity.
One other DIY NAS out there is openfiler.com and it appears that they are about to release v2.1 of their distro. MSFT makes a 'Windows Storage Server' that just got updated to v2.0, but it's currently available to OEM builders only, not DIY fans.