It's a few weeks since I installed SqueezeCenter 7.2 on my mini Linux server. I'm delighted to say that it's working out great.
Music playback on my Squeezebox player is flawless. The responsiveness of the player and web interface is just fine.
My server is the recently released fit-PC Slim (512MB RAM), which I ordered diskless and fitted with a 250GB disk. It's running a minimal server install of Ubuntu 8.04 with a few services including SqueezeCenter.
In its current configuration, my fit-PC draws just 7 watts.
I think that's pretty terrific. I expect to get the power consumption even lower whenever I get around to disabling the WIFI adapter in the BIOS.
I only have one Squeezebox, so can't comment on the ability to serve multiple clients, though I have played to the Squeezebox and my laptop simultaneously without glitches. Also, no problem streaming music while performing other background tasks, like copying on new music files and transcoding from FLAC to mp3.
I reckon the fit-PC is a really great fit for SqueezeCenter.