Just in case you haven't noticed it yet: Petr Lapukhov wrote a great (and very long) article describing MSTP. It covers everything, from the basics to multi-region design and interoperability issues. Highly recommended reading.
Ivan Pepelnjak, CCIE#1354, is the chief technology advisor for NIL Data Communications. He has been designing and implementing large-scale data communications networks as well as teaching and writing books about advanced technologies since 1990. See his full profile, contact him or follow @ioshints on Twitter.