A lazy reading on the web seems to suggest that the grass isn’t any more greener in the OpenStack camp when handling KVM host failures. See this earlier blog post for context.
Update (20140114): I have tested KVM HA on Apache CloudStack 4.2.1 and its functioning as expected. Please see this new blog post.
The Linux Kernel Virtual Machine (KVM) is a very popular hypervisor choice amongst CloudStack and OpenStack users. It is free and comes ready with popular Linux distributions like CentOS/RedHat and Ubuntu. In some cases, customers insist on using and end to end Open Source solution for their private cloud and KVM ends up being the only choice available.
I recently had an opportunity to hook up Apache CloudStack 4.1 to Active Directory via OpenLDAP Proxies. While the OpenLDAP installation and configuration is relatively simple if you have prior experience with LDAP, the actual CloudStack configuration to use LDAP authentication is even simpler.