The host said that it was "extraordinary" to have girlband Little Mix in the Wembley showdown, described Marcus Collins as "consistent" and that it was "great to see Amelia Lily come back" following her early exit from the show.
O'Leary also claimed that the move to Wembley Arena and the judges' duets would ensure that this year's finale was something to "really look forward to".
Gary Barlow has described this year's showdown as "the biggest final ever", while Kelly Rowland promised that the acts would "blow everyone away".
The X Factor final kicks off on Saturday (December 10) at 8pm on ITV1.
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