I don't really consider Nick Knight to be part of the A-star line-up, so although he's undoubtedly tedious, I wouldn't say he's my answer to this question.
As usual with Sky, their coverage of cricket is phenomenal and I like pretty much all of their commentators. Bob Willis is possibly my favourite pundit on any channel and for any sport. The way he just tears into people is wonderful to watch. In the commentary team, I think Atherton is the best technically, and Botham, Bumble, Warne and Nasser are quite fun and easy to listen to as they don't seem to take it too seriously. Strauss has also been a good addition for the reasons mentioned above by other people. If I had to pick a weak link, I'd probably go for Michael Holding, who seems to be anti-England at times and doesn't really say anything even an unqualified pleb like me couldn't offer.
I wouldn't say 'anti-England', just NOT 'pro-England'. Which is presumably the POINT of having a non-English pundit on the team?