Ferdinand isn't too bad imo. He got better during the WC the longer it went on, he just seemed to relax into it a little bit more. He is a hugely experienced player, whose opinion you could respect compared to Robbie "I once played for Utd" Savage for example.
Phil Neville is ok too. [Poor language removed] voice like and should swerve commentary duties.
I think defenders generally make better pundits, especially during tactical breakdowns, which is why Sky is good as they have lots of time to do this. Defenders have to read the game better, whereas a lot of attackers games are built on unpredictability. Watch Shearer try to back up a point he makes. He almost always just says "Well, I disagree. I think he should be there instead" etc but has no reason for it.