There's a running joke around the office that if you have two SharePoint references, one of them MSDN and the other a blog post, and the two differ, then the blog post must be correct.
Seriously, having been weaned on the excellent documentation for .NET and SQL Server, I must say I am VERY disappointed in the lack of documentation on MSDN for the SharePoint API and XML schemas. MOSS is already over a year old (in its final version, 90% of the API is probably 2 years old (or older)), MS not having proper documentation for the product at this point is inexcusable.
That said, almost as bad is the lack of community involvement on the MSDN pseudo-wiki. Surely many a SharePoint developer has figured out what is really going on behind say, the SPContentType.Hidden property, but where is the user-contributed content? If you figure something out, and it's not documented, post it.