I've been seeing quite an uptick in the people that are wanting to install Solaris 11 when they are doing hardware refreshes.  I applaud that effort - Solaris 11 (and 11.1) have great improvements that advance the state of the art and make the best use of the latest hardware.

Sometimes, however, you really don't want to disturb the OS or upgrade to the a later version of an application that is certified with Solaris 11.  That's a great use of Solaris 10 Zones.  If you are already using Solaris Cluster, or would like to have more protection as you put more eggs in an ever growing basket, check out solaris10 Brand Zone Clusters.