Yeah, it's hard to see what Nadella's leadership has actually added to MS from where I've standing. As best as I can tell, there hasn't been any major new products or shifts since Ballmer left. People talk about MS "stagnating" under Ballmer, and that's true of the stock price, but revenue and profit more than doubled under Ballmer and he introduced multiple new billion-dollar products/services. Nadella has made some notable acquisitions (LinkedIn, Github, Minecraft), but I'm not real sure that these are really winners from a business perspective, aside from Minecraft.

Sure, Ballmer had failures too - Windows Phone and Zune didn't take off. But you can't win every time.

EDIT: Sorry, was lazy and abbreviated Windows Phone to WP.