I work around big machines all day with tons of fan noise, so I think thats one of the reasons I am going smaller at home. If I need a ton of storage, a server is always somewhere on the network that can have more drives added. And it's noise is isolated to the basement. Plus, all the LAN parties I attend (and some I don't sue to the hassle) will be easier with a tiny case.

As far as RAID 1, the onboard motherboard one should be fine. But, one big disadvantage I see is if it fails, and the motherboard is no longer made, finding a compatible solution to get your data back could be a problem.