Good luck to them. Linux and Apple need some snappy competition, they're getting lazy. Also, it would be nice if (for the first time in recorded history) all the major OSes didn't suck.
In general, Microsoft has too many PMs. While many PMs do incredibly valuable work, many are simply an added layer of indirection and approval to hinder progress. My understanding is that there was a time at Microsoft where the "dual ladders" broke down and people had to switch from Dev to PM or individual contributor to people manager in order to make more money. It appears that Stephen Sinofski has reversed that trend in the Windows organization and is shifting power and decision making back to the developers while rewarding them without regard for their number of reports. Windows is a big product built by a big team. These things take time, so this triad concept seems like a pretty good stepping stone.
I'm sold!