I think most people would agree, even those who flat out say they hate John Cena's guts, that Cena's matches on Raw have been stellar as United States Champion.
I can understand people not being into Cena's character all that much; it's virtually unchanged over the past decade and it doesn't help but a strong argument can be made that he's heavily overexposed. At the same time, I also can understand why WWE has stuck with Cena's formula because it's been a proven money-maker and making money is the name of the game, not catering to smarks.
A lot of people have maintained that Cena "can't wrestle" even though it's an absurd notion. Cena's had too many great matches over the years with too many different opponents; I've seen matches in which one guy is carried by the other one, we all have at some point, and that's never been the case with Cena. Over the past 4 months or so, however, Cena has put on performances that have once again not only proven that he can wrestle, but the performances have been of such quality that the only ones who still hold onto this notion are those who're just simply determined to hate any & all things associated with John Cena.
Another thing that's helped Cena is that he's felt fresher than he has in many a year due in part to spending so much time out of the main event title scene while simultaneously helping to build up a desperately flagging United States Championship picture. Off and on, there've been a few threads pop up over the years stating that main eventers should win the mid-card titles to build them up and, while an interesting notion, it's not one that we ever really thought would happen in Vince McMahon's WWE.