Hamilton's performance in GP2 in 2006 and F1 over the last two years clearly show that he is one of the best around at the moment.
I really don't get this "arrogant" thing that keeps coming up as a reason to "hate" him, or call him an idiot. All racing drivers are arrogant; some more obviously than others.
Schumacher was obnoxiously arrogant, even in his early days. In his Ferrari era he thought he deserved wins even when his team-mate had pulled over to let him pass. Senna was famous for it. "But I am Senna!" he once declared as an excuse for why he could behave differently to other drivers. It was this attitude that made them the Champions that they became. Hamilton would never have got this far without the same attitude.
I remember Ralf S constantly making the most ridiculous claims about his own ability, he also once said that he would not let anybody else overtake him again. Even at the end of his F1 career he was still claiming to be one of the fastest drivers despite seasons of evidence to the contrary. He sticks in my mind because I never had a high opinion of him, but there have been many other similar cases. Every single one of those backmarkers being outperformed by their own team-mate thinks that they could win the WDC in the right car.
It seems to me that there are three main groups of people complaining about Hamilton's arrogance. There's the hardcore Nando fans who are angry that Lewis showed up their man last season. There's a few hardcore Ferrari fans who hate Hamilton just like they hate Alonso, for challenging Ferrari. And then there's the racists, who say things like "Hamilton should know his place"; they're upset that one of the last strongholds of whites-only sport has been broken and he won't even toodle around at the back like a black man should!