Forum OpenACS Q&A: Re: OpenVZ
The one thing that a zone cannot do is run a different version of the OS - that is, each zone can only be a Solaris 10 instance.
However, OS patches, new packages, etc. can be installed once and made available to all instances immediately; and the disk space used is the space taken by the package, plus a few KBytes for each zones package database.
And yes, inittab works properly inside a Solaris zone, unlike the possibly strange behavior you will run into under a vserver.