I've only been doing clipless for a week and a half and I already get in and out without thinking. It's very easy. But you can get flustered/disoriented. There's no reason, even at a dead stop while falling, that you can't unclip. Except that we tend to instinctively want to slide out feet outward instead of twist them when panicked. Which wouldn't be any different with toeclips. You'd still have to take an unusual motion to free yourself; whether you learn that motion with toeclips or clipless.