In pre-1.4.3, falling velocity has decreased. When falling from let's say Y=263 to Y=63, in 1.4.2 it will take ~4 seconds, whereas in pre-1.4.3 the same things takes ~10 seconds.

When reproducing, it is important to fly higher than Y=254 (when the biome info in the debugging/F3 screen disappears. For some reason in 1.4.3 you have a significant slow falling velocity as long as you are above Y=254.