I like Sue Perkins too (although her eye makeup/false eyelashes gets on my nerves because it makes her eyes look droopy - hope it's not due to her brain tumour), but I suspect she's on the show simply because she's part of the Mel and Sue comedy duo. They are part of the show for me, although I thought they were a waste of space at first.
Actually if anyone has got on my nerves this series, it's Paul. I think he's going out of his way to be more negative, to the point where Mary is obviously trying to compensate for him. It's always been a good cop bad cop partnership, but this series he seems to be pushing the Simon Cowell impression too far.