Even better, it looks like Solars 10 Update 6 will contain this functionality, according to a Sun presentation:
ZFS Root (S10 Update 6)
● Brings all the ZFS goodness to /
● Checksums, compression, replication, snapshots and clones
● Boot from any dataset
● Patching becomes safe
● Take snapshot, apply patch... rollback if you don't like it
● Live upgrade becomes fast
● Create clone (instant), upgrade, boot from clone
● No “extra partition”
● 10U6:Based on new Solaris boot arch.
● ZFS can easily create multiple boot environments
● GRUB can easily manage them
The whole presentation is here.
I cant wait to to apply my first set of patches, or perform a upgrade on a ZFS snapshot. Or why not daily snapshot of / and perhaps before you install that 3rd party software....
Easy, cheap, fast and safe modifications to the OS and boot environment!