I have had a few hours to try the final Solaris 11 release, overall I think it is far more stable and polished than the previous "Early Adaptors" release. Besides the fact that I am unable to use semi-old SPARC gear to test the release since only the latest generations of hardware are supported I have found few real problem so far.
The new packaging system finally fixes what I believe have been the biggest problem for Solaris the last five years or so, it is now repository based and it is simple to install software and dependencies are automatically solved. No more hassle of downloading and installing multiple software packages from SunFreeware to resolve dependencies. This also makes packaging faster and safer, brining the whole system to a known level and always with a safe recover option since it is used in conjunction with ZFS clones.
Zones are a fantastic tool for security/workload separation and virtualization so it's good to see that so many enhancements have been done in this area. The perhaps most noticeable is of corse that they now also use the new IPS system for packages and that makes a vanilla zones very lightweight without the hassle of a sparse zone. NFS service can now finally be provided from inside a zone. There is a tight integration with the new crossbow network virtualization making is possible to limit bandwidth to zones, use DHCP in a zone without having a separate NIC and build internal networks between zones inside a single Solaris 11 instance.
Imagine the power and flexibility of an T4-4 with 256 CPU threads and 1TB of memory running 50 zones with several high bandwidth/low latency networks inside the machine with no latency or overhead caused by virtualization.
Unfortunately the X86 version with the graphical desktop seems to be somewhat unstable compared to the Express release, I think it's related to the upgrade of the X server. I have been unable to use my laptop with to displays with the final release.
Solaris 11 is however focused on usage in servers and it seems stable for that, I have only found one disturbing problem so far, sharing ZFS filesystems does not seem to work ( zfs set -o sharenfs=on), but you can share each individual filesystem with the share command. Sadly if you are evaluating this you will probably have to wait until next year when there is a full release of Solaris since no updates are provided without a service contract. If you work for Oracle this is something you might want to fix for everyone, or tell me what I'm doing wrong.
Solaris 11 have many other new features such as per-user encryption of home directories with ZFS crypto, a new mirror/raidz hybrid bloc allocator for ZFS, numerous security enhancements among other thinks. I have only named a few of the changes I will probably keep posting Solaris 11 stuff as I find something interesting that is not directly highlighted it Oracle own what's new documents.
Update: As pointed out in the comments sharing of NFS together with ZFS works a bit differently now. If you share an existing dataset you have to set the share property. However if you set the sharenfs property when creating the dataset it works as in previous versions of Solaris 11 Express, OpenSolaris etc. Move information available in the documentation here.
Talks I have given
3 months ago