All good stuff, but...
..surely the biggest opportunity for power saving is passive (or lower energy) data centre cooling? I know there's been some fancy work on passively cooled data centres, and on using lakes or rivers as heat sinks, but that's not mainstream (yet).
Starting off with the sort of poorly ventilated shed that most DC's appear to sit in is a rather poor start for thermal management, but I'll forego the temptation to suggest simplistic cooling solutions about which I know nothing; Even so, the inherent waste and cost of air conditioning really needs to be a major target, as that's probably two or three times the power costs of the actual racks?