How can I check what system updates I've installed on my Mac?

Now that's an interesting theory that I haven't heard before. If anything, reading sites like MacFixIt and MacInTouch seem to suggest the opposite: that sometimes the little incremental releases can have unintended problems that are often ironed out by the time you get to a bigger system release.

Be that as it may -- and if you, dear reader, have any theories either way, do chime in with a comment -- there are a couple of ways to see what you have installed on your Mac OS X system. The easiest way is to just launch Apple --> System Preferences... and choose "Software Update". You'll see this:

Notice the two quasi-tabs along the middle of the window. We're looking at "Scheduled Check". Instead, click on "Installed Updates" and here's what you'll see:

As you can see, I have dutifully installed quite a few incremental updates to individual applications, not just the omnibus updaters that Apple occasionally releases. I'll draw particular attention to the entry on 2/21/08, however, as that is one of those "get everything up-to-date" updates. It's labeled "Mac OS X Update ... 10.5.2" and it's the fact that there isn't an individual application named that you know it applies to multiple apps.

There are also "Security Updates" and generally while I think that the Mac is far less susceptible to hacker attacks, I still encourage you to apply these whenever you see one appear in the Software Update window.

One more note: the log file shows you oldest to newest, if you're looking at the version numbers and wondering what's going on (like the update to 10.5.2 even though the current version of Mac OS X is 10.5.3).