O'Neill was critical of the state of the playing surface at Wembley during the 2-1 defeat to Manchester United in the Carling Cup final, claiming there "was no excuse" for the poor conditions.
But he is happy to be returning to the national stadium after Villa's superb second-half show against Reading.
O'Neill said: "It's great to be back at Wembley again - even on that pitch.
"I didn't enjoy the occasion at all last week so there is a chance to put that right now.
"It took us time today before we treated it like a quarter-final in the FA Cup.
"You need character and determination to fight and we didn't have that in the first half.
"But it came back in great abundance.
"It's fantastic for the football club to be in the semi-finals and I genuinely feel for the supporters. They were fantastic.
"Even at 2-0 down to a Championship club they were cheering us on and that was a big boost."
Villa were staring at an upset when Shane Long's two goals put the Royals in control at the break but Ashley Young pulled one back within two minutes of the restart to get them back in it.
Carew then scored twice in the space of six minutes to put Villa ahead before the hour mark before capping the win with a penalty in stoppage-time.
Now, O'Neill has challenged the Norway striker to maintain that form for the rest of the season.
He said: "Gabriel Agbonlahor was poorly this morning and had to go home so John steps in and scores a second-half hat-trick which was absolutely delightful.
"John at his hungriest can perform like that.
"He got the equaliser for us and his game lifted two or three-fold.
"Goals give him confidence and the next thing you know he is running the game. He can do that and I want him to perform like that more often.
"I would be delighted if he could score a hat-trick every week but first he needs to find a level of performance which is up there with the best strikers."
Villa's run to the Carling Cup final saw an even more thrilling game when Blackburn were beaten 6-4 in the semi-final, and O'Neill conceded his side had produced some dramatic football in the cups this season.
He said: "There have been some great games this season and that is what cup football is about.
"We go for it and so have other teams against us. Reading's part shouldn't be underplayed.
"They were fantastic and played it like a quarter-final from the first whistle. They were terrific."
Reading boss Brian McDermott, meanwhile, reserved praise for goalscorer Long, who had sat out the previous four games through suspension following a red card in the fifth-round tie with West Brom.
First he headed in after Matt Mills had flicked on a corner, and the Republic of Ireland international then swept home a second after a fine passing move.
McDermott said: "Shane scored twice against international defenders and he was first-class throughout.
"I am very proud of all my players. I am disappointed for the fans that we couldn't get a day out at Wembley but we must now focus on the league.
"We came up against players who could be in the Champions League next year.
"They have pace, power and quality all over the pitch and I think we gave them as tough a game as they have had all season."
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