Can I bring my ol' 486 down from the cupboard to give it a go?
Hehe, that might be a little optimistic
The big reason for having it CLI based is to limit bloat and overhead. I'd imagine there'd also be some benefit in power consumption. What makes Ubuntu Server better than, say, FreeNAS is that you have infinite flexibility. Yes, it's not as pretty or straightforward, but once you can copy what someone else did, it should do much easier. Another thing that irked me with FreeNAS was that you were buggered with bleeding edge hardware. Because FreeNAS was a generation behind on BSD you were forced to use older hardware to make sure the OS supports it. With Ubuntu it'll support whatever is out there, there's no abstraction between you and the OS.
I figured this should resonate with a bunch of you here, esp those running Media streamers and squeezeboxes. This is about as frugal as you can go for an always-on solution.
For reference, I've gone for a build that'll use as little power as possible. I'm using a Celeron 430 CPU, this has a total TDP of around 40W if I'm not mistaken. When idle, the CPU draws less than half that. I still need to measure the consumption, but I think I'm at around 40W in total for the whole box. This includes the 4 2TB HDD's and 2GB of RAM. I'm still experimenting with getting the drives to spin down as well to save me that extra little bit of juice.