After a dismal run to the World Cup, Steve Hansen's side were revived in Australia, giving New Zealand and England a severe scare before eventually going out at the quarter-final stage.
Wales proved those two performances were no fluke with a clinical dismissal of Scotland in their opening game last week and they head to the Irish capital in confident mood as they look to end a run of four successive defeats at the hands of their hosts.
As a close friend of Hansen, who will leave his job at the end of the competition to take up a post as assistant to All Blacks coach Graham Henry, O'Sullivan has been delighted at Wales' stunning transformation.
And he believes the sight of the red dragon roaring again can only be good for the game as a whole.
"We have to recognise that Wales are a completely different side to the one they were 12 months ago and that has to be good news for rugby," said O'Sullivan.
"The Six Nations is the benchmark for the sport in this part of the world and what we don't want is for the tournament to be won by England or France every year with all the other countries struggling behind.
"That is a big challenge because we know France and England have great strength in depth and they are both very good sides.
"But it is great to see Wales back and we want to keep the challenge up as well."
While the majority of the rugby public have been amazed at Wales' sudden change in fortune, O'Sullivan is not surprised.
Once peace broke out in the club game and Hansen was given the domestic structure he was looking for, the Irish coach believes it was only a matter of time before the rejuvenation began.
"I respect Steve a lot," said O'Sullivan. "He is a good coach and is finally getting things done the way he wants them.
"He has been through a tough time and Wales went into the World Cup with everyone expecting them to do badly.
"That took the pressure off them. They went out and played rugby and maintained that level of performance against Scotland.
"Maybe at times they have got their selection or their tactics wrong but Wales have always produced rugby players.
"At the moment they have got a good blend. They have a coach who has them focussed and they are playing confidently."
Ireland's chances of bouncing back from Saturday's 35-17 reverse in Paris have been boosted by some good news on the injury front.
While talisman Brian O'Driscoll has recovered from the hamstring injury which prevented him from travelling to France, Wales will be without skipper Colin Charvis who dislocated a finger against the Scots.
The presence of O'Driscoll in the home ranks is bound to have a positive impact and, coupled with Charvis' absence, will fuel belief that the Irish are set to record their customary win.
However, O'Sullivan is urging caution and warned his players that any drop in standard will result in an unnecessary defeat.
"Just because we have beaten Wales the last few times doesn't mean we have any divine right to do so again," he said.
"We will have to play well to win and if we don't we will come out on the wrong side of the result."