I was pleasantly surprised to see a new icon on my top panel today - the update notifier .
Clicking on it opened the Update Manager, which you can also access from the System > Administration menu:
Selecting Update All notified me that a new Boot Environment was going to be created. This is great as I don't have to worry about these updates somehow harming my system.
The update took a couple of minutes to complete:
After which I rebooted. There was a new opensolaris-1 grub menu item, which was the default. I'm now up to date.