But for all that good form on the road, coach O'Sullivan is delighted to be closing out the campaign in Dublin on Sunday.
"Away games are very difficult in the Six Nations," he said.
"The 50,000 people at Lansdowne Road on Sunday will be a factor.
"The support we've got has been unbelievable. It makes the players six inches taller, two seconds faster and makes them hit 10 kilos heavier."
That said, the Irish coach is in no way under-estimating the size of the task - especially after the scare they had at the Millennium Stadium last Saturday when edging out Wales by a point.
"England are the best team in the world, though, without a shadow of a doubt," he added.
"They're coming into our backyard, and we're looking forward to the challenge. Sunday's game will be like a chess game, played on adrenaline.
"Our job on Sunday is to play to our potential. We can't turn them into supermen - but if we give the performance of our lives England will have to play out of their shirts."