For people being familiar with Terminal.app or the UNIX side of OS X there is no need to reinstall the system or restore everything from backup. All the "Thunderbolt update 1.2" replaces is this single kernel extension:
/System/Library/Extensions/IONetworkingFamily.kext/Contents/PlugIns/AppleBCM5701 Ethernet.kext
There are no pre-/postscript scripts included in the installer so all it needs in case you're affected by the kernel panic is to restore this kext from its original state before.
In case you have a recent TimeMachine Backup simply pull the kext folder out of the backup after booting from the recovery partition (using cmd-r at boot). Or tar/untar it from another machine with 10.7.4.
You could even use the kext from the recovery partition itself. But then you should apply the 10.7.4 combo update after the next reboot because the AppleBCM5701Ethernet.kext on the recovery partition is from August 2011 whereas the AppleBCM5701Ethernet.kext when applied Thunderbolt update 1.1 is from 29th April 2012.