Sun has released Solaris 10 8/07 (aka update 4) into the wild. You can grab a copy for yourself from the download site.

There are a lot of enhancements and some new functionality in this release. Most notably IP Instances, so each of your zones can have their own IP stack, and Branded Zones, which allows you to install CentOS 3.5-3.8 or Red Hat Enterprise Linux 3.5-3.8 inside a non-global zone, and then run Linux userland applications (list of applications reported to work), unmodified, within a zone on your Solaris host.

You can find a full list of changes in the "What's New" document on docs.sun.com.

Kernel update patches are due to follow shortly.