Cook is going to be great or terrible based on the metrics you apply. It's such a vast entity, you can have all range of opinions, and be able to defend them.
I'll say this. The hardware is behind. They know that. Intel got behind, and I think you're going to see that never happen again. Tim Cook's time at the top has had him not utterly tank the business Steve rebuilt. As someone following a cult icon, that's actually better than expected. I really truly believe his tenure is going to be defined by the next six months. I have the money to buy a new machine. Will I want to? Millions of people are about to make a purchase decision on the iPhone 7, missing a 3.5mm jack. Will they balk at it?
In the end, the "lead" has been ceded to Samsung and Huawei on hardware, but not on software. That "few years ahead of the competition" is a memory now. Computers are not always a spec war, but they do have to be compelling. And for everyone who got on that "iPhone every year" nonsense, good luck with all those headphone dongles.
Ultimately, 2017 is either going to be one of Apple's finer years, or the Grace Period is going to be nearly over. I know I removed 2/3 of my exposure to AAPL ahead of this iPhone launch... so, so many good and bad things going on with Apple today, no polar opinions seem appropriate. Just remember, inspiration gets pushed into the pipeline years before the magic is public. As such, this is Tim's time now. Let's see how 2016 finishes.