With their previously weak scrum now being lauded as a set piece weapon and despite being down to only 13 men at one stage, Australia fired a warning shot that Henry said the All Blacks will have stood up and taken note of.
"I think they are probably playing their best rugby for 15 years since they won the World Cup in '99 when John Eales was the captain and had the Bledisloe Cup that time too," Henry said. "They are starting to look quite threatening really.
"I think we saw this morning with their defence, that's the sign of a side with character and togetherness and that hasn't been there for some time. They are the side that has probably come the furtherest and improved the most during this Rugby World Cup and this year. They've got it together, they've got a good culture."
Henry said the win helped Australia onto "the good side of the draw where they won't get smashed about".
"They will get Scotland in the quarter which is the soft game of the quarters with all due respect to Scotland, so they're guaranteed a semi final place, most likely against Ireland.
"So they are not going to get smashed around next week and are looking good for the semi-finals - and who knows beyond that."
The 2011 World Cup-winning All Blacks coach also threw a curve ball by favouring Ireland to defeat France this morning - a result that would pitch the Frenchmen against New Zealand in a Cardiff quarter final and leave the Irish facing Argentina in another quarter final.
Henry pointed out Argentina had beaten France in the bronze medal play-off in the 2007 World Cup, again in a group match in 2011 and once more last year in France. He felt the Tricolours found the Pumas such difficult opposition they would probably prefer to face the All Blacks instead next week.
"There's a French psyche that doesn't like playing Argentina so I just wonder if they might be a bit indifferent going into tomorrow morning's game about the result (against Ireland)," he said. "(Whereas) I don't think they mind playing the All Blacks. You look back to 1999. I think something happened in 2007 as well. So the French have got a bit of history in World Cups played in the northern hemisphere and I think they will feel more comfortable playing the All Blacks than they would playing Argentina."
Henry felt Argentina were the other rugby nation that had come on in leaps and bounds in recent years and had been impressed with their Cup performances, pointing out they stretched the All Blacks and had put big scores up against other group rivals.
Henry also believed Wales were a good chance of beating South Africa in the quarter finals despite their ongoing injury problems and the loss to Australia.
He felt Warren Gatland's men has shown real "resilience" and that the tough group matches to date would help the Welsh compared to the Springboks who had come through a "soft pool".
"South Africa are improving," he said. "They are starting to look a wee bit better. I still think they're too old in the tight five. I think they might get found out defensively there.
"I don't see them as real contenders. I think they have probably got too many players who have been there a long time and are probably going down the other side of the hill....I think the Welsh will give them a huge game."
He encouraged All Blacks supporters to take heart despite some anxiety over the pool matches including Saturday morning's last group encounter against Tonga.
He expected the All Blacks to play a more territory-based game plan now they were into the knockout stages of the tournaments.
"They will be on the job. They will be on the edge of the edge and that's exactly where they need to be. I think Steve (Hansen) and company will be pretty happy with where they are at. They haven't hit their straps. They've struggled to get their game together in total so they won't have got ahead of themselves.
"I can remember in 2007, we beat the Italians by 90 in the first game, we beat Portugal by 100, somebody else by about 100 and we played Scotland B. So we had no football going into that French game in 2007. The teams we had played against were not good opposition. We gave them all hidings, we looked good and probably got ahead of ourselves.
"There's no way this side will get ahead of themselves, so that's an ideal situation."
