The GP Power Tools includes all of the functionality of the old Support Debugging Tool that they replace, but have new functionality, enhancements and bug fixes.
There is a special introductory annual subscription price of US$365 (one free day every four years!).
More information can be found on the GP Power Tools here.
That said, you should consider upgrading to GP Power Tools for one major benefit: GP Power Tools is fully supported by Winthrop DC.
While this may not sound like much, the old Support Debugging Tool, which was offered by Microsoft, was not supported at all (not even by Microsoft).