My criticism of him has always been centred around his pathetic off-the-ball contribution. On the ball he is a competant technical player, nothing more. I'm still yet to see why he is so grossly overrated or what exactly "ticking over" constitutes. He usually has very little impact on games and is a complete passenger more often than not.
When he actually plays well, like he did in that little run of games including Cardiff, Newcastle, Man United etc. we all noticed and praised him for it. The reason many people don't most the time is because he is totally anonymous. The problem though is people have been so taken in by the "unseen work" mantra that any anonymous performance is automatically deemed acceptable under the guise of this.
It was the same with Petrov during the O'Neill days, I always thought he was the obvious weak-link in that midfield but his inclusion was excused on for the same reasons that Westwood's is.
Petrov was massively under-rated when he played for us. His game was to break up play and give the ball to one of our attacking players, in the season before he got sick he had started adding goals to his game and was a top quality player for us for a few seasons, alot of fans only realised how important and good he was after he was gone.