ESXi in a Nutshell
- Live migrations of running VMs between hosts to limit downtime
- Low performance impact from virtualization layer on running VMs
- Management tools/vCenter make managing multiple VMs easy
- Guest OS support
Cons
- Cost to get all the features you want, e.g. Live Migration
- Fat client required to manage individual hosts (getting better with some web consoles currently in development by VMware Labs)
- Not as robust without a vCenter implementation