Button’s had a much better year than people expected him to. He’s beaten Lewis outright for pace on occasion, he’s been the cleverer and more reliable driver most of the time, and he’s been a stand up man for the team. I think that most people would say that Lewis has better raw speed than he does, but Lewis also has better raw speed than just about every driver on the grid, so I don’t see that as a damning factor against him.
Given that he’s a new driver in the team, that Nick Fry’s petty behaviour stopped him coming into the team when the car design was still being finalised and developed (to the point where he still wasn’t fitting into it properly at the first race), that he’s had at least 3 different race engineers, and that the McLaren has been a gripless car that doesn’t like the bumps (even Lewis has been complaining of lack of grip), I think he’s done a solid job.
My criticism of him would be that on the occasions when he’s been off the pace, or Lewis has had the run on him, he’s been far too comfortable about that fact and hasn’t been pushing hard enough.
Interestingly, Button has always complained about lack of grip and heat in the tyres. I wonder if Ferrari, who have always had excellent mechanical grip, might make a better team for him? Of course, with Alonso there, Ferrari is a bad team for any driver not called Alonso.