Kernel zones are a mature technology and are already in production for many large and criticial customer systems. We have customers who have switched from LDOMs to Kernel Zones and use live migration on similar SPARC systems to those you list.
It is highly recommended that you use 11.4.1 and configure memory reservation pools feature if you use kernel zones, this is important when you run a mix of kernel and native (or solaris10 brand) zones or any other applications in the hosting global zone.
Darren J Moffat
Oracle Solaris Engineering - Software Architect