Because of the re-partition needed with this firmware, fully charged the battery, wiped caches and factory re-set and such before flashing. Odin flash process was quick and painless. Rooted with Chainfire's mod and reinstalled apps with TB. Left the data as I'd had issues with restoring app data in the past.
It's smooth, touchscreen sensitivity is back to pre-JVH levels and is a delight to use. I see new system icons and some other visual improvements.
Too early to give a full verdict on performance, but wiping emails, something that used to take between 3 and 5 seconds, is now around a second.
So it's like having a new phone. Once again, it's a vanilla experience with only the rooted kernel as a hack.
Nice work Google and Sammy.