The December cumulative update that was released on the 18th of December 2008 has been re-released. There were many reports amongst the community of errors involved during the update. I myself ran into the old 'Upgrade failed to initialize' error that ocured after running the SharePoint Products and Technologies Configuration Wizard. Lucky I ran this update in a test environment first. Microsoft have also stated that it is recommended to wait till SharePoint SP2 which will be released early next year.
I found the Cumulative Update a good option if you haven't installed the infrastructure update yet, as this update includes the infrastructure update.
As always make sure you have installed Service pack 1 for WSS 3.0 and MOSS 2007 (if you are running MOSS 2007).
Here are the December Updates:
Windows SharePoint Services 3.0 December Cumulative Update
Microsoft Office SharePoint Server 2007 December Cumulative Update
You can find the Microsoft SharePoint team blog post regarding this here: