Although 2010/11 was a disappointing season for Munster in Europe, Saturday's triumph was fitting reward for a superb Magners League campaign which saw McGahan's men finish 13 points clear at the top of the table. And, given that the Australian used more than 50 players in the 24 games, beating Leinster was tangible proof of the success of his player development policy.
"It's huge right across the board," said McGahan. "From the playing group, the management and the organisation to development officers, young players coming through and, more importantly, the supporters, they can look around now and say that we have done something very important.
"From a Magners League perspective, we played 24 games, 21 results. To get through such a tough season with a small population base and dealing with the national side is difficult but it certainly gives us the opportunity to do that and we still have got plenty more to come," added McGahan, who said he was delighted at the progress of younger players such as Conor Murray, Danny Barnes and Mike Sherry.
"We are delighted but we didn't need this victory to prove that to us, we knew they would be ready. There was no bigger stage than against, without a doubt, the best side in Europe, and to stand up and contribute to the result is fantastic news for everyone involved."
If there were words for the next generation, McGahan also took time out to salute 37-year-old prop John Hayes, the oldest player on the pitch, who played the full 80 minutes and was part of a Munster scrum that secured a penalty try to seal victory.
"Absolutely incredible isn't it? We keep a pretty close eye on him to see how he's moving around and he was like a young man. For him to finish off the game and get a penalty try against a quality scrum and play out the 80, what a fantastic tribute," enthused McGahan.
Leinster coach Joe Schmidt was understandably deflated at not being able to round off his debut season with an historic double.
"Fatigue was a factor, we made a few changes because guys were out on their feet," said Schmidt.
"I felt they (Munster) needed it more than we wanted it and they showed a hell of a lot of character.
"I spoke to the team in the dressing-room and said: 'Lads, this is the little bit of bitterness that we need to store away for next season but I want you to reflect on the season as a whole, the effort and the energy that you have thrown into it and you can look back with a fair bit of credit on what you have achieved'."
Captain Leo Cullen said that, once the pain of this defeat had worn off, Leinster would be able to reflect on a successful season.
"Last week was great, this week not so great. Seven days is a long time and, right now, it's hard to remember last week, but I'm sure over the next couple of days it will sink in that we have had a very good year.
"But right now, I have pretty mixed emotions, I'm tired and looking for a rest, but I'll have to cheer up, I'm getting married next week so I'll have to change focus."