Re: Easiest Home File Server OS?
At the end of the day pretty much *any* major OS written in the last 10 years can function as some form of file server, and if you're not expecting blistering performance and don't need any features beyond "here's a network volume where I can dump stuff and get stuff", all will do the job pretty much identically.
However, as far as "one size fits all" solutions go, I'd recommend FreeNAS. The disadvantage is that not being a general purpose OS you can't really (well you can, but it's tricky) use it for much else - however since you're dealing with rather underpowered boxes, that may be a bit of a blessing in disguise. It's simple to set up, powerful, supports pretty much everything you could want or care about (and a lot more besides) and has been going for a while now (so is pretty darn stable.)
Save the whales, feed the hungry, free the mallocs.