Like Philipp, I just noticed that the new simplified 2013 build templates still don't provide an obvious way to prevent a gated checkin build from appending "**NO_CI**" to the checkin comment, preventing subsequent continuous integration or rolling builds from running.
I had a look around and discovered that rather than the old SyncWorkspace activity, the new TfGetSources activity looks like the right place to go to:
I was slightly confused, as reviewing the current class documentation doesn't list the property. And it turns out that indeed for TFS 2013 RTM, this property didn't exist (I found this out the hard way – a workflow that references that property will fail when run on such an environment).
Comparing the two C:\Program Files\Microsoft Team Foundation Server 12.0\Tools\Microsoft.TeamFoundation.Build.Activities.dll files (from two different machines) in Reflector reveals the following:
A useful change introduced in Update 2.