I love this quote taken from information week
In its initial iteration, vSphere 4 can manage up to 1,280 virtual machines on 32 servers, or an average 40 VMs per server. Each server may have up to 64 cores, such as eight-way server with eight cores per CPU, for a total of 2,048 cores; each server may host 32 TB of RAM. VSphere 4 can also manage 8,000 network ports and 16 PB of storage.
and this one:
Network throughput is now 30 Gbps compared with the previous 9 Gbps. A virtual machine can have up to 300,000 operations per second versus 100,000, and the new maximum number of transactions per second is 8,900. The latter figure is five times the total transactions per second of the Visa network worldwide, said Steve Herrod, CTO of VMware. VSphere 4 includes Distributed Power Management, which monitors running virtual machines and moves them off underutilized servers, which is shut down, to a server running closer to capacity. By adopting Distributed Power Management, a VMware customer can save 20% of his power consumption, said Herrod. If all VMware customers implemented it, the saved power would be enough to supply the nation of Denmark for 10 days, he claimed. He then quipped it would be enough to serve Las Vegas for nine minutes. VSphere 4 includes VMware Host Profiles, which are golden images of desired server configurations. By referring to a host profile, a vSphere user can generate a new virtual machine and know its properties, according to Herrod.