A public service announcement for Sharepoint 2013 customers:
Our colleagues in CTS note (and reminded us) that the Sharepoint March 2013 Public Updates will be required for future Cumulative Updates – that is, they form the new servicing baseline for Sharepoint 2013.
Important: Due to a change in the package configuration introduced after SharePoint 2013 RTM the March Public update is a mandatory requirement in order to install subsequent SharePoint 2013 Updates.
In Common Question: What is the difference between a PU, a CU and a COD, Stefan Gossner (please forgive the anglicization) covers the difference between Sharepoint update types.
When to install: As a PU includes security fixes it is recommended to evaluate and install PUs as soon as possible.
Impact on future fixes: In some situations a PU can be a prerequisite of future CUs and PUs. E.g. the March 2013 PU for SharePoint 2013 will be a prerequisite for all future CUs (and potentially PUs) for SharePoint 2013.
Finally, Russ Maxwell has a tip (actually a Powershell script) on reducing the amount of time it takes to install a CU by stopping services first, too.
Posted by Tristan Kington, MSPFE Editor on a mission to civilize