Not that other major characters are not without powerful motive. As Tyrion aptly says, everyone other than Cersei, who if nothing else loves her children, is suspect. Certainly Stannis Baratheon is well served by Joffrey's demise, and, who knows, maybe that worm he consigned to the flames had some magical effect. And Olenna articulated the benefits of Joffrey's death to her granddaughter - though we learn that because she didn't consummate her marriage with Joffrey, she's not really a full-fledged queen.
The most interesting developments continue to be in King's Landing, though we got some good scenes with Daenerys and in two places up North. But Tywin's prepping of Joffrey's young brother for kingship, Jaime and Cersei, and most of all the progression of Tyrion for trial were all primo.
Again, I haven't read beyond the first novel, and the television series has shown us there's no telling about what might occur, so we have to assume that Tyrion is in real danger, even though he's the best character in the narrative. Will Tywin let his son be put to death - much as his son's an embarrassment - and even though Tywin, savvy as he his, must know that it wasn't Tyrion who did the deed? Probably not, but I wouldn't bet on it. Jaime wouldn't ordinarily let his brother be killed either - and he stands up for Tyrion to Cersei - but he's pretty much indicated in the past that he'd do anything for Cersei. Has he changed so much that his devotion now has limits? Also hard to say, and he does certainly still desire Cersei.
Season 4 is shaping up as the best season so far, with riveting story lines in the center and all the peripheries.
See also Games of Thrones Season 4 Premiere: Salient Points ... Game of Thrones 4.2: Whodunnit?
And see also Game of Thrones Back in Play for Season 2 ... Game of Thrones 2.2: Cersei vs. Tyrion
And see also A Game of Thrones: My 1996 Review of the First Novel ... Game of Thrones Begins Greatly on HBO ... Game of Thrones 1.2: Prince, Wolf, Bastard, Dwarf ... Games of Thrones 1.3: Genuine Demons ... Game of Thrones 1.4: Broken Things ... Game of Thrones 1.5: Ned Under Seige ... Game of Thrones 1.6: Molten Ever After ... Games of Thrones 1.7: Swiveling Pieces ... Game of Thrones 1.8: Star Wars of the Realms ... Game of Thrones 1.9: Is Ned Really Dead? ... Game of Thrones 1.10 Meets True Blood
And here's a Spanish article in Semana, the leading news magazine in Colombia, in which I'm quoted about explicit sex on television, including on Game of Thrones.
And see "'Game of Thrones': Why the Buzz is So Big" article in The Christian Science Monitor, 8 April 2014, with my quotes.
"I was here, in Carthage, three months from now."