Kevin Doyle and Alex Pearce scored to send Ireland into their Euro 2016 qualifying campaign on a positive note.
And O'Neill feels the match will have been hugely beneficial for the likes of Doyle and Darron Gibson, who have not featured domestically so far this season.
"You could see that the game was important to us because some players definitely needed it," he said. "Darron Gibson was getting very tired because he has trained with Everton all pre-season but he hasn't actually played a competitive game.
"There were a number of players in the same boat and I think it showed."
But O'Neill stressed the importance of getting up to speed quickly ahead of Sunday's opening qualifier in Georgia.
"We had plenty of possession and we played some nice stuff but we weren't really able to finish it off," he continued. "In the dressing room, the players said that there are improvements in this side.
"We think that, but time is pressing and we have that big game on Sunday."
O'Neill made six substitutions during the course of the second half, and the 67-year-old believes the replacements gave his side the required lift to put the game to bed.
"I thought when the substitutions came on they gave us a little more life and energy and a little more impact," he added. "We maybe scored the second goal because of that.
"It was important for us to win the game because it gave us a bit of confidence."
"Despite the fact that we can improve, I thought we were reasonably comfortable without that real incision but you can say that is the history of the Republic [of Ireland]."
