10.6.4 is out, and the moon didn't change to green cheese

Question

Remember everyone, 10.6.4 is software, and therefore it can't "cause" hardware to fail.
Remember 10.6.4 may have been under testing by many developers, but there is no guarantee your software was tested by that developer with the latest seed, until after its actual release.
What does that mean to the uninitiated in people doing software updates:
1. Don't become the first guinea pig on the block, unless you are prepared. This means steps 2 and following:
2. Backup your data at least twice.
3. Contact all your software developers websites or phone numbers
to see if the release has been checked and hardware driver developers.
4. Give yourself sufficient hard disk space to maneuver.
5. Dismount and disconnect all non-Apple peripherals. That means keyboards, mice, printers, scanners, etc...
6. Repair permissions for good measure before and after. This voodoo trick sometimes actually has helped updaters. Applications -> Utilities -> Disk Utility.
7. Check your Audio Midi Setup Utility didn't reset itself in Applications -> Utilities on Sound output after the update. Sometimes changing the frequency solves volume issues on select applications.
8. Don't expect the update to perform any magic for which it was not documented to help. It may be "recommended for all users", but really, it is "recommended for all users who are ready to have the latest and greatest."
9. Zap your PRAM:
http://docs.info.apple.com/article.html?artnum=2238
This Voodoo trick has helped many others.
10. If uncertain ask here in the forum with a new topic thread here:
http://discussions.apple.com/forum.jspa?forumID=1337&start=0
If you just attach your post to another thread, few others will see it, and you won't likely be helping the person starting that topic thread.

Answer 1

The moon may not have turned to cheese but your memory has. Past OS updates have, in fact, "Caused" hardware to fail. OEM Memory upgrades working fine but going "bad" because they were slightly out of spec after an OS update and hard disk boot records getting clobbered are two examples that come to mind. Arguably, a device driver broken from an API change rendering the device dead for all intents and purposes has been "caused" to fail.
That said, the Mac OS is the best computing platform in the world and Software Update, as magical as it is, still manifests itself as yet another system nag. The fact that OS updates are mixed in with Java, Quicktime and other component updates will always create the opportunity for users to fail to perform all the prescribed Voodoo in this thread.
It is therefore incumbent upon the Mac priesthood of gurus such as yourself and others to be vigilant and patiently help ferret out the tangled problems that can and do occur when OS updates go amuck.
For those in such a place, the self-healing capability of 10.6 may be all the voodoo needed:
http://www.go-go-godzilla.com/self-healingSnowLeopard.html