I noticed that Apple claims this is a "critical security issue". Leaving aside how long it has taken for Apple to eventually notice a problem (especially if the word "critical" comes up in a discussion), I was wondering how critical is this fix considering every user does have the option to turn off this time/date network checking in the Date/Time preference pane at any time. I am assuming turning off (once the date and time has been checked, of course) would avoid all manner of nasties from third-party attackers. For this issue to suddenly crop up at this time would suggest either a lot of users are leaving the feature turned on as if that extra level of accuracy is critical in people's lives and could make the difference as to whether or not people make it to their all-important meeting etc, or Apple is trying to look like it is doing a fantastic job at finding security problems and fixing them promptly during this Christmas festive season.
Not sure which is closer to the truth.
At any rate, the fact that Apple has provided a fix (better late than never) and I have found no problems so far during the installation means I'll give this software a good rating.