Are people running large KVM Clusters?

Just curious to see the size of KVM proxmox installs and what sort of backing hardware people are using. Any large farms out there? how are you finding proxmox as a management tool? do you rely on the built in backup or roll your own?

Looking at a smallish setup my self.
Two of the following servers:
- Xenon E5-2620
- 32GB ECC RAM
- Server Board with twin nics, GB Ethenet
- 128GB SSD, for OS only

VM Storage:
QNAP NAS
- 6TB (Raid 10)
- NFS Shares

Running around 5 Windows Servers, low load.