Starting on March 14, 2013, Microsoft started offering SQL Server 2012 Service Pack 1 as an Optional update on Microsoft Update (as shown in Figure 1). That means that it will not be pushed down automatically, and you will not even see it unless you are running Microsoft Update (which is an optional superset of Windows Update).
Figure 1: SQL Server 2012 Service Pack 1 on Microsoft Update
Personally, I like the fact that more people will be reminded about SQL Server 2012 Service Pack 1 (as long as they are running Microsoft Update), but I still think it is better to manually download and install SQL Server 2012 Service Pack 1 yourself, rather than pulling it down from Microsoft Update. I think that database professionals should maintain their SQL Server instances explicitly, by design.
If you are going to move to the SQL Server 2012 Service Pack 1 branch, I think you should make sure to also install SQL Server 2012 Service Pack 1 Cumulative Update 3 while you are at it. Microsoft has been very busy fixing many important issues (and actually adding some new functionality) with the early CUs for SQL Server 2012.