KDE hangs a few seconds during startup. It does that every time.
Accourding to  it is because of some sound issue. Disabling kmixd system service solved it for me.
Steps to Reproduce:
2. Login again a notice the pause in the startup.
The system stalls for a few seconds.
The system should continue without stalling.
Accouding to  it could be related to specifics in the sound hardware. So not everyone migt experience it. For the record I amd running KDE on a Lenovo T430S
Fixed for KDE 4.13
Do you have a commit link ?
It still hangs in 4.12.95
Basically deleting /etc/xdg/autostart/pulseaudio.desktop removes the problem.
About the commit link. I was pretty sure it was the DBUS/MPRIS2 issue, which took several commits. Here is the link to the last commit and the ticket:
*** This bug has been marked as a duplicate of bug 317926 ***