In the books Cersei is the Queen Regent and Joffrey has no power over her until he becomes an adult. However, she still has difficulties keeping him under control.

In the TV show, presumably to ramp up tension, they seem to have made Joffrey old enough that he can rule as King directly, and can even order and threaten Cersei around. Which is a bit lazy, to be honest. The way the books do it is more interesting, and prevents Joffrey from turning into a totally pantomime/cartoon villain, which I think this approach risks.

Other than that, mostly I liked it. Melisandre is different from the book's interpretation, a little bit weirder and more offbeat. Liam Cunningham is excellent as Davos, though he's not had much to do so far. The red comet as a scene transition device was also pretty cool, although it could get overused if it happens every week.