I'm not going to put this post in spoilers because the thread title already did that job. Silly people spoiling posts in a spoiler thread. :P
This was a great setup episode for the major plotlines of the season going forward. It wasn't the best for plot or character development, but it served a very good purpose.
It was kind of necessary after they threw so many twists and new developments at us at the end of last season: Sansa and Theon Reek escaping, Cersei getting freed, Myrcella dying, Arya going blind, Danaerys getting snagged by a khalasar, Tyrion apparently set to try to rule Mereen with Varys and Grey Worm, Stannis maybe dying (still yet to be confirmed), and Jon Snow getting shanked. Seriously, that was a lot of stuff to drop at the end of the season. They needed to pick all those threads back up and reacquaint the average viewer with them, because most people will just go into it without rewatching the last season or reading one of those refresher guides that show up everywhere on the internet before popular shows return for a new season and the show runners want even those plebs to be able to follow along with the basic plot points. It's standard practice in TV. The show ought to pick up pace from here onward, now that they've gotten the recap material out of the way and given most of those plotlines a step forward.
Hell, some of them took huge leaps forward, particularly the Dorne plot. I'm not particularly fond of the Sand Snakes, but holy shit are they rushing that plot forward. That's the kind of shit you'd expect near the end of a season for most shows, not in the opening episode. Brienne and Sansa finally linking up is also a pretty big deal, especially if all the speculation I've seen about Stannis still being alive turns out to be true. Melisandre turning out to be a rather old woman using a glamour to take on the look of a seductress was neat, shows she can do truly magical things other than make shadow babies, and that magic of hers will certainly have an impact on the stuff going on at the Wall.
Then, if all that isn't enough to get you excited for the rest of the season, there are still two big plotlines that should be showing up next episode: Bran and his warg shenanigans, and the Ironborn finally doing something other than being mentioned.
Overall I liked the episode for what it was, and I'm more hyped than ever to see what comes next.