To pschaff: I am very sorry, you are absolutely right.
Now I will try to correct my answer.
When I was tried to setup oVirt some times ago, I found that the existing in repositories version of vdsm (4.9-63) intend for RHEV-M version 2.2.
In process of installation oVirt create default cluster which has compatibility with new version (3) of virtualisation manager engine (oVirt or RHEV-M).
In case of different versions of engine defined for cluster and really installed on hosts you can get that message ("Host's Compatibility Version doesn't match ...").
To test newest versions of oVirt and vdsm on CentOS 6.2, I am builded my own rpm from git sources. If you want, I can get you link for my test repository.