I just got the Pdf and I must say to the developers thank you for making some metamagics prerequisites for other powers. It just makes beter sense to have one power before the other. Its something that I felt that sr3 latched because when the rules offered certain varient powers I alwayed wandered why take then over the root.

Actually several SR3 metamagics already featured prerequisite / advanced metamagics, although admittedly this wasn't as clearly set out as it is now in Street Magic or organized in quite the same way.