The Hardware: Verizon Galaxy S3 16GB SCH-i535 (Pebble Blue, if you must know )
Where I was: Rooted Stock ICS 4.0.4 (Root66) VRALF2 with OTA blocker to keep it there.
What I did first:
Unblocked OTA updates.
First update 40MB VRALF2 to VRALG7. Updated succeeded but broke root. Restored Root using Voodoo OTA Rootkeeper
Second Update: 62MB VRALG7 to VRALHE. Updated succeeded but broke root again. Got a Custom Padlock screen on bootup that wouldn't go away even if the phone was not rooted before the upgrade. Restored Root using Voodoo OTA Rootkeeper.
Third Update: 400MB VRALHE to VRBLK3. Update FAILED. Repeatedly. Each time, the update would download and reboot into recovery mode to install. It would get about 40% of the way through and the widdle gween andwoid would fall over with a yellow twiangle above him. Then it would reboot back into VRALHE.
What I did next:
ODIN flashed back to VRALF2 Root66
Took OTA updates.
First succeeded as before, so did the second. To my surprise the third ran to completion. Restored Root using Voodoo OTA Rootkeeper. Still has a custom padlock on boot, but when I unlocked the bootloader it disappeared - either that or the boot screen didn't stay on long enough for it to appear - not sure which.
Anyway, I am now on JB. The last to the party. as usual. Project butter must have worked - the interface feels smoother.
Battery life is a mixed bag. I use Battery Widget Reborn Pro to measure the average time to use 1% of battery life. Under ICS it was 6-9 minutes. On initially installing Jelly Bean, this initially dropped to about 3 minutes. I assumed that this was because of post-upgrade housekeeping, as the CPU was continuously busy (according to Usage Timelines Pro). After leaving it running and on the charger all night long, it settled down. It is now at 10-15 minutes per 1% of battery life - almost double what I was getting before.
OTA blocker supports VRALF2 and VRALG7, but it does NOT support VRALHE or VRBLK3. This is not surprising; the last version is three months old. With no OTA Blocker, I am at the mercy of whatever method Verizon comes up with to bugger up my phone. The OTA blocker folks need to get their fingers out and update the app.
On the other hand, the folks who built Voodoo OTA Rootkeeper (which I originally bought for my Droid X2) are on the ball and they have saved my bacon thus far.
Hope this helps anyone out there in a similar predicament. The usual caveat applies: Before trying anything drastic, BACK UP YOUR DATA!
Finally I would like to recognize two apps that have been very useful to me during this process: I have no interest in either developer or program, just a satisfied customer.
Usage Timelines -- A neat program that tells you how busy your CPU is (Free, full version is $2.49)
EZ Recovery -- on-the-fly recovery flash of CWM, CWM Touch, TWRP, Stock or... just about anything else. (Free, but I sent the dev a few dollars)