Hostbill works great and has the features, just not the management that is required to succeed.
h34r: Proxmox is great and stable, solusvm has its plus as well as onapp but let me ask a question would you rather have HA that works correctly and the ability to run both KVM and openvz on one system. Proxmox 3.0 has the cloning and template features added now and works great haven't had issues yet. Not to mention quick install, multi-master node, stable and open source, great community support as well as paid support if required. Security is the main thing I will always request in a CMS first then everything else follows.