Examples of rough edges in .NET I pointed out are removed in the next version of .NET framework (aka Whidbey).  It will come with concrete classes that reduces provider-specific dependencies.

Don't expect magic though.  Provider-specific SQL syntaxes are not going away anytime soon.  While storing SQL statements in external configuration files is the obvious solution, there are associated security risks.  Digitally signed configuration files offers some protection, but it's a hassle to implement and takes away much of the power of configuration files.

I am looking at System.DirectoryServices namespace right now.  It looks to be equivalent of Java's JNDI package.  I am not yet sure how it handles in-memory objects (i.e. data sources) bound to the directory service.  Still moving.