In reply to aln:
It's quite uncomfortable listening, isn't it?
I know these things take a while to bed-in but Simon Mayo is sharp, quick-witted, a good interviewer and, what I think is essential for a DJ/radio presenter, he 'knows his music'. Jo Whiley is pleasant enough but, when on her previous evening show, she often seemed to be a bit awkward sometimes, especially with guests, and when having to think of something off-the-cuff and she'd often fail to follow up on what could be an interesting point made by a guest. This is still apparent in the joint show but, unfortunately, seems to have stifled SM a little.
Her music knowledge doesn't seem to be as wide-ranging as it could/should be: on her previous show she played tracks that almost anyone -certainly a national presenter- would reasonably be expected to know and she'd get a word or two wrong of either the song name or performer. It was as if she'd had to read the info rather than just knowing it. I can't quote any examples, but it was noticeable a few times. I think they were 60s or 70s tracks so maybe she's more at home with indie and Britpop onwards from her Radio 1 days with Steve Lurpak. Simon May, in contrast, seems to have a solid music knowledge.
As Summo said, this is apparently because of equality - well, you can't get more equal than a 1:1 ratio of male and female presenters on a show, can you? I wonder if it has been done as JW requested different hours? Fair enough if it has, but it's not resulted an improved listening experience.