I think he's great. I think his knowledge is being kept up to date (he has been out in the 2010 Ferrari, which means he has driven a more recent F1 car than DC!). His grid walks are great as he has far more access through sheer bloody mindedness than anyone else. And Sky have F1 rights untill 2017 at least (I can't see them dropping it then either), so he has another 5 years minimum.
That's not assured at all. Just look at how quickly the terms of BBC's contract got ripped up and replaced just 3 years in.
If the great Sky gamble doesn't pay off for Bernie then that too can be ripped up and replaced just as quickly...