After installing it, booting took much longer, I had severe flickering in Safari (Videos and Flash content), some resolution problems with the secondary display and worst of all, VLC wouldn't play any video. Took me some time to nail it down to the security update 2015-001, but after restoring a system backup with TM, everything was normal again. Tried installing the update manually and repaired permissions before and after (as suggested somewhere else, I don't believe in it), but same problem.
So now I'm without security update 2015-001 and I'm wondering how I can safely install it.
So I waited and now Security Update 2015-002 came out. Software Update didn't offer me the 001 any more, so I tried the 002. Same problems after installing. So I reinstalled all drivers/patches from Multibeast and the system worked fine again after reboot.