He's legendary for being Bill's bulldog, and aggressively convincing people to buy Bill's solutions. Whether he was qualified to lead a technical organization like Microsoft on his own, as Bill's successor? Ehhhhh... maybe?

You know that "used car salesman" persona that he had in that internal Windows 1.0 video (https://www.youtube.com/watch?v=DgJS2tQPGKQ)? That's kind of his business strategy -- sell, sell, sell, push, push, push. Don't let potential clients say "no" to Microsoft products. And when you're an aggressive company like Microsoft, you want that in an exec -- but not necessarily a CEO who's in charge of managing the technical developments also. So I think he was really competent and essential to Microsoft's success, even if he didn't make such a good CEO.

(Fun fact: I used to think that the character Palmer from Final Fantasy VII, a member of Shinra Company's executive leadership, was a parody of Steve Ballmer himself based on his name, appearance, and goofy mannerisms. I'm no longer convinced this is the case, but it's a pretty funny coincidence.)