I can answer that one.

I'm on Stock ROM, unlocked (sometimes I lock it back with BootUnlocker [which is the tool you mentioned] which does not wipe data, requires root) and currently on custom kernel (was still on stock kernel few days back)

So, if google releases OTA update and you are on stock ROM, unlocked; you can directly update (the second N4 I had on hand did not update to 4.2.1 when I rooted it. I only OTA-update it after I root + unlock my device).

As for when you're on custom kernel, I'm not sure if OTA still works but the second-best way I could think of is to flash a stock-reset kernel (to revert back to stock kernel), OTA-update, and re-flash custom kernels.

Added these to FAQ's

Thanks guys!

is there any apps to unlocked the phone by swiping the screen without rooting the device?

http://tamagotchilife.com/app-download/

cannot download this apps
why this happen? i want play tamgothi 

i found out y i didn't get the OTA notice even after clearing the service framework.  after i disable it and enable it back, i got the OTA notification immediately.

strange why we have to do this to get the update, shouldn't it work without all the hassle?

Sometime between last night and this morning, my 2 week old Nexus 4 died on me.  Last night I plugged it in to charge and the normal Time - Date - Charging - Little Padlock screen appears.

This morning I went to unplug it and the phone was Off/Dead (which is strange cause why should it be off?).  So I pressed the On button but a strange totally white battery shape icon appears for 2 seconds and then the phone dies again. I think I repeated this process repeatedly for 10 minutes and the same thing happen again and again.  Naturally I was very distressed.  However, on the last attempt to turn it on, the phone actually turned on > asked for password > then OK already.....phew.....what do you guys think happened?  I didnt download any apps the last few days except 2 days ago i updated to android 4.2.2

If any of you guys wanna try Ubuntu Touch Preview, Droid-Life have a guide flashing it using custom recovery. On XDA, some reported stuck during booting after wiping and some claimed that worked properly without wiping. Anyway, try at your own risk:

Droid-Life: http://www.droid-life.com/2013/02/21/how-t...ustom-recovery/
XDA discussion thread: http://forum.xda-developers.com/showthread.php?t=2078727

Because it's Ubuntu. Very popular Linux OS for PC and notebook. Now ubuntu can run in various type of device from pc to smartphone. the UI is beautiful.