I'd say Tim Cook is a decent care-taker CEO, but not one that seems to have great vision or drive.
Yes, Apple has enjoyed a lot of successes financially under him, but most of the grunt work was done by Steve.
Look at some of the missteps under his leadership.
Apple Maps is an unmitigated failure, one that should have not seen the light of day. Beta testers of iOS 6 were quite vocal in stating its lack of finish, but they rolled something out that was incomplete and buggy.
Hiring Browett, all I can say for someone who's supposed to be a supply chain genius and one who has his pulse on the apple stores, he screwed this up big. No way should he have been hired
I'm not sure if its really his "mistake" but I'll mention it. Why in the world would you roll out a thin iMac, I mean it just sits on the desk, and because of the components its only thin from one angle, you cannot help but see the bulge in the back.
Siri has not really been the success it should have been, though this may have been partly on Job's watch I'm not sure about the timing.