Affects Version/s: Minecraft 15w42a
Fix Version/s: None
Environment:Java Version 8 Update 60 (build 1.8.0_60-b27)
It is not possible to control tamed horses anymore even with a saddle. It seemed to work in 40b. It also appears impossible to tame a horse, it will run around but never throw you off and will never be tamed.
Load map from 40b.
Find tamed horse with saddle.
Can't control it, it won't move.
(optional) remove saddle, add it back. Still won't move.
Spawn horse with mob-egg.
Jump on it.
It will not be tamed and you won't get thrown off. It will still run around like when you jump on an untamed horse in previous editions.