I am optimistic with slight reservation.
I think the main concern, and the only valid one I can think of, is the issue of aboveground vs underground bitcoin. Bitcoin grows by either the quiet growth within the community, and/or by the expansion of that very community out and into the public sphere. Clearly with this decision, the top players in this community have placed their bets with growth by publicity. They must recognize however, that with the benefits of greater publicity and assertiveness comes the perils of aggressive action by those actors who see bitcoin as a threat. I think such a foundation was inevitable, but some might say that it should have waited until more "quiet" development had occurred.
As for the other concerns expressed in this thread:
1. The Foundation is asserting itself as the official voice of bitcoin, when a collection of "unofficial" voices is safer when dealing with a legally ambiguous entity.
1a. Essentially the same as above. There is a strategic give and take between streamlining bitcoin's interaction with a society that is potentially benign and fielding inquiries from a system that is potentially hostile. Evidently the Foundation thinks it is worth the risk.
2. Democracy is ineffective in ascertaining the official voice of the community.
2a. The Foundation will need to answer questions as to the workings of their alleged democratic system. If the community grows dissatisfied with how the Foundation is portraying bitcoin, and the Foundation takes the classic democratic turn towards oligarchy, then alternative "official" voices and associations will certainly spring forth and return us to a more decentralized balance.
3. Regulators will compromise the Foundation and ruin bitcoin!
3a. If they wished to do so pre-Foundation, they would go after Gavin directly. Now, supported by a Foundation with money and lawyers, Gavin and the other developers are much better protected from such dangers, and able to generate an appropriate response (or a fork) if need be. Besides, the nature of the satoshi protocol contains numerous safeguards built-in against such kinds of "attacks" (namely that bitcoin versions are voluntary downloads). At the same time, government interference is arguably more likely now that bitcoin is growing out in the open.
Unless Gavin accepts the "long-arm of government" through the "official" voice of The Bitcoin Foundation. Before you know it, you'll see government backdoors in the protocol and people would be swayed into accepting it with little question because "Standards".