Most of my criticisms with Braga and Trek had to do with his writing and story ideas, not his production talents. The with the development of Cosmos being handled by Druyan and Tyson (among others) I'm not worried about Braga. If you haven't already, you can get your actor-hosting-science-show fix with Morgan Freeman's Through the Wormhole - which is actually a really good series. And, to me, it's exactly why Tyson is the right person for Cosmos. Freeman often adds his own commentary into the episodes - literally injecting his voice into the narrative. It works because Freeman is curious and his ability to tie his own experiences and curiosity to the subject matter helps the series feel like it's exploring big questions. Cosmos, though, was originally Sagan's personal journey. Quite simply, no one can replace his voice in the series because they aren't Sagan. But if you're going to replace him, you'd better do so with someone who has a similar breadth and depth of knowledge, optimism in humanity, and interest in making science exploration accessible. Tyson certainly fits that description.