[JohnBooty]

I feel like each feature has it's own story (and it's own party to blame, when some browsers support it but not others)

If FF is lagging behind Safari on a particular CSS feature that certainly points to FF being behind the curve.

Sometimes it's FF or Safari simply being slower than Google. Sometimes it's a matter of the Chrome team creating an implementation of feature XYZ and getting it minted into the standard so of course they have the only implementation for a while.

Sometimes the FF and Safari teams have specific objections to a feature, often because unlike Google they actually consider user privacy a core part of their mission. Although, of course, with CSS features... that's not gonna be a privacy thing.