From my perspective it is missing a couple of other things vs. a homegrown WHS box, especially if you want to use it as a PVR – my WHS box has 6 hard drives and runs SageTV to act as the backbone of a whole-house PVR solution.
What I would want that this server doesn’t have:
Firewire – to change channels on your cable boxes or, potentially, use for video with R5000 boxes.
Internal slots for TV tuners
More than 4 USB ports for USB tuners (HD-PVRs, etc), external hard drives, etc.
A faster CPU to be able to do stuff like run commercial skipping apps.
More memory.
.
