Joel's latest article - How Microsoft Lost the API War - is up and, as always, is a great read.
As a framework developer, I've dealt with similar issues on a smaller scale. The classic 'silver bullet' syndrome - starting from scratch may eliminate the current set of problems but invariably adds a few new ones of its own. (I particularly liked Joel's analogy about RSS and ATOM in this regard).
One thing I've learned: It's better to be extensible than comprehensive.