I'm December filer, sent 129F on 12/5 and got my alien registration number changed on 12/17/13. Now I'm waiting for NOA2. When reading lots of posts and checking Igor's list, I'm wondering if CSC has slowed down their K-1 processing since very few cases got approved recently.
I also checked the USCIS status of "batch" group around my receipt number and see most of us are in "Initial Review".
Hope all filers get approved soon!