I think the incremental improvements in safety with state-of-the-art ideal practice in carseats are often over-represented and miscalculated in the scheme of things (especially with respect to the quality of the driver, especialy when the kid is crying).
The real problem with car seats as I see it is that life doesn't always fit into the rigid guidelines that policy makers prefer. A fairy doesn't cast a spell that imparts sufficient neck strength for them to safely face forward on the eve of their first birthday.
We've applied common sense to err on both sides of our local law. We put DD in a forward-facing seat before the law allowed because she'd outgrown the rear-facing seat. Now she's old enough and large enough to legally eschew the booster seat, but she's still in one, because otherwise the shoulder strap is over her neck.
Of course, policy-makers make rigid guidelines because too many people can't be trusted to exercise common sense. I once met a woman who moved her toddler to the front seat because he was fussy. She was cited for it, and she had no idea why. The consequences of an under-height passenger and an airbag deployment were already common knowledge by then.
