He's been getting steadily better over the last few months but, as with most things, there's been ups and downs along the way. He was poor against City but he was very good in the two games I mentioned above.
There are other examples, too, going back even further. I actually think his best performance of the season was arguably WBA away. Although that probably stands out because most of his team-mates didn't play very well and he seemed to take it on himself to beat them single-handedly.
EDIT: Blackburn and Valencia are also good examples, as Treble said.
Of course there are some examples in there but his form hasn't been consistently good. However he seems a different player altogether again now that Hernandez is stretching the opposition and allowing him space to work in, surely you have all noticed that too?