Here are my small complaints:
I'm surprised with how Euron managed to built such a big armada that can shoot fireballs and have amazing decorations so quickly. Not only that, he managed to move all his ships without getting noticed by anyone in Dragonstone, nevertheless, he apparently knew exactly where Dany's fleet was going and got there very quickly.
I think this was the writers doing their best to weaken Dany's army quickly just so we can start worrying about Dany losing against Cersei. So much hype for the alliance between Yara and Dany and now it's all gone in just one episode. I still loved that battle though!
Also, about the arguments that Cersei uses to convince the other lords, I thought it was okay, but it still didn't convince me completely.
If Tarly actually respected Lady Olenna and his alliance with House Tyrell, then why the hell did he decided to meet up with Cersei in the first place? Why didn't he join House Tyrell as soon as he heard that Cersei burned Mace Tyrell, Loras, Margaery and a bunch of innocent people? He's scared that Cersei might kill him? Oh please, the probability of Dany killing him is way higher if he decided to join Cersei, plus, didn't he fought for the targaryens before?
That scene between Missandei and Greyworm was unnecessary, it should've ended with just a kiss, I really wanted it to end quickly.
Edit: Sorry if this is nitpicking.