* a couple with "cannot mount /efs" errors have fixed their device by flashing ics. If you know you haven't got a VTU00M eMMC firmware 0xf1 - go for it. However for those of you who don't know, this would be extremely dangerous. You could get SDS so I do not recommend this action. If you are foolish enough to try it, flash 4.1.2 immediately afterwards.
2) /efs partition format changed
A quick note before going forward... when looking at a ROM build number, the last 3 characters mean Year, Month, Revision. Let's take XXEMG4 for example. M = 2013, G = July, 4 = revision 4. See "Other" section at the end of this post for more info
From July 2013 (XXEMG4) onwards, official Samsung ROMs change the format of your EFS Directory/Partition. Let's say these ROMs change from EFS v1 to EFS v2. Only basebands from July 2013 (MG2) onwards can read EFS v2.