Couple of thoughts on Argentina:
Fantastic defence, obviously. But they weren't able to get out of defence, reason being they lacked two important things - 1) aggressive defence, big, momentum-changing tackles behind the gainline which breaks down the flow of the attack and / or leads to turnovers; the Argentinian defence is more based around making tackle after tackle after tackle but the trouble with that is eventually the attack will wear you down. 2) A better kicking game. They need an alternative to kicking the ball straight back to the opposition. Also there's a lot of pressure on Sanchez to do the clearing kicks, a scrumhalf needs to be able to clear from the base when close to the tryline. They play too uch rugby around their own 22, and I think a lot of the reason for this is not having an effective kicking game.
They really do have some quality back three players around. All three looked good today, Imhoff's defence seems to have been approved and he has the potential to be one of the top wingers in the world (I'd pick him over Savea at the moment, certainly), Tuculet is very classy, Cordero's a livewire and had a couple of really good takes today.
Creevy is the best hooker in the world.
Hernandez is going to give away at least one try this tournament with one of those round the back passes. Look great, but for the love of God do it in the right areas of the field