The "Customize your feed" forum preferences don't do anything for me, even after clicking the save them all sub forums still show up. This problem is present in both Firefox and Chrome browsers for me (win7).
Here's an example.
I have reported this problem back when the new sire launched and the issue is still present, nor has there been any reply another time it was posted. Now that Rorie is around people are getting a bit more replies so I though it might be worth a shot to bring it up again.