Sad to lose him. It's not an easy gig - as Steve Jones proved Stateside; rumour has it he wanted to go to the US show and Cowell insisted he was needed in the UK. Even Ant and Dec can't touch him IMO. If he gets a Hollie Steel or Rachel Crow situation, he can handle it.
Olly and Caroline were excellent on ITV2 so I'd be quite happy to see them on the main show. I'm not convinced it needs someone really rehearsed and slick like Dermot was; take the Davina approach in the early series of Big Brother and have a duo as into the show as the core viewership... if they were going to have another duo, Stephen Mulhern and Emma Willus are a good call for Xtra Factor. Or continuing the Heart theme, possibly JK and Lucy from London drivetime/network Saturday breakfast.
I will never be able to understand why Steve Jones was picked to move to the US; he wasn't exactly crème de la crème material over here. I always thought he was poor; even Gethin Jones would be a wiser choice.
Quite how anyone could say Dermot O'Dreary trumps Ant and Dec is beyond me. I'm not sure I like any of his ex-T4 brethren either.