I thought it was a very good episode, nice warm up to open out the season and get our engines revving to enjoy the rest to come.
Though that being said I have not read the books (I can definitely appreciate that as a fan of a book series the screen adaptation will nearly always disappoint - see LOTR, Happy Potter, Eragon ect)
I felt that the Dorne story has been a little lacking compared to others, but I've generally enjoyed it (though again I don't know what I'm missing so) and felt pretty excited when the snakes killed Doran and Trystane, though was hoping Trystane would put up a bit more of a fight. Looking forwards to whatever conflict and hopefully war that arises because of that. (Also I thought Trystane was in a room that looked a little like a boat, or if it was a boat then you'd assume it was docked in Dorne, otherwise they'd of established it being elsewhere). - I remembered.
If you want to talk about frustrating inconstancies then where did the hounds that were after Reek and Sansa go when they were attacked? They magically vanished to leave the humans to fight it out, it seems.
My advice is to consider the series separate from the books, especially since they are differing so much from what I hear. On there own its pretty damn amazing IMO.