Storage is key - wonder why EMC picked up this little startup called VMware ? Well, they realized when you distill down (target 20:1 consolidation ratio) the relatively fast and under utilitied CPU and memory resources in a datacenter, those will scale fine as long as the centralized storage is 1st tier enterprise class.
IOPs
latency
snapshots
data replication
DR
data de-dup
mutlti-tier (FC, SATA)
the server technology: choose your best of breed commodity CPU and memory, while the storage will be require the most discerning analysis for some time to come.
stay tuned...