There isn't much to the EXT4 updates for Linux 4.3 besides clean-ups and fixes. Ted Ts'o wrote in the pull request, "Pretty much all bug fixes and clean ups for 4.3, after a lot of features and other churn going into 4.2."
On a related note, Jens Axboe sent in the core block I/O and block driver updates for Linux 4.3. Those too aren't too exciting but mostly routine work. Yesterday was also the already covered F2FS file-system update.
Meanwhile, the debate over removing the EXT3 driver for Linux 4.3 is still ongoing.
There's daily Git benchmarks of different systems with the XFS/EXT4/Btrfs file-systems over on LinuxBenchmarking.com.