You will need some hard checkpoints. In my opinion, a widely disbursed and actively staked coin does not need a checkpoint server. So the centralization would come from the source code, just like the protocol rules do for every coin.

Charles's absence from the new leadership team has no impact on the ether sale or the timeline of the Ethereum genesis block launch or its feature set; if you want to see how progress on actually building Ethereum is going, the only place where you can really see that is simply by looking at the level of activity on our github repos (my own efforts have been focused on the serpent/cpp branch, allowing Gav and Jeff to easily integrate Serpent compilation into their C++ and Go clients). We are not aware of the details of what Charles is now working on, but we wish him well.