Hot but her voice is grating. When I watch her, I see an anchor/host who only talks on one speed and one volume. Quick and medium-loud. She's always on about an 8 and I think she would be best served with a co-host or political sidekick to play off of.
Quick and medium-loud is no way to go through a 60-minute show every night. I actually find some of the other blond anchors in the FOX stable easier to watch/listen to when they sub in, particularly Martha MacCallum. She can be intense and also dial it back. Kelly just hits the viewer with a hammer over .... and over.
Megyn Kelly has solid ratings for cable in that time slot but that's out of default. I think when she was on O'Reilly, she was a strong guest but being a strong guest doesn't always translate into being a strong host.