I think that he's good... but too young. He's a bit too young to experience the pressure* that Toro Rosso puts on its drivers and he might be a tad reckless on the start. On the other hand, he knows the Hungaroring and his results seem to indicate he's quite talented. By the way, he is improving considerably in World Series by Renault, although his teammate (Oliver Turvey) seems to have adapted better.
I'd finally like to say that I'm wary. It seems very likely to me that if he doesn't have a Vettel second half, his F1 chances will considerably diminish, something sad for a promising 19 year old driver.
* Regarding pressure, Alonso once said that the pressure in F1 is nothing compared to what he used to feel in the lower categories, when not winning could easily mean an early end to his career.
I am not amazed by F1 cars in Monaco. I want to see them driving in the A8 highway: Variable radius corners, negative banking, and extreme narrowings that Tilke has never dreamed off. Oh, yes, and "beautiful" weather tops it all.
"Prediction is very difficult, especially about the future." Niels Bohr