I'm a little surprised there have been so few posts about On Stranger Tides, but my reaction in short was: I enjoyed it, but it didn't give me the same sense of excitement that the first and to some extent the second movie did. A few more spoilery thoughts under the cut. Also, there are spoilers in the comments.
Having been reassured by
geekmama that there were no references to the previous movies, I attempted to view OST as something completely separate, and it works well as a standalone movie, a fun piratey adventure.
Jack takes center stage this time, and he's in fine form. I loved his interaction with Barbossa, who starts out in a place I wouldn't have expected (much like I didn't expect the change in Norrington's situation in DMC). But he's still Barbossa (apples!) and he has some wonderful scenes, especially one conversation with Jack near the end. I had hoped for a glimpse of Jack the Monkey, too, and my wish came true in that regard :-)
I also very much enjoyed the friendship between Jack and Gibbs, and it was wonderful to have Gibbs back. I can't imagine a PotC movie without him, it just wouldn't be right.
I missed seeing the Pearl in action, and would have liked there to be more ships in general. It was a nice change of pace with the scenes in London, though, where Judi Dench made a brief but memorable appearance!
As for Gillette and Groves... what a sad, meaningless waste of characters. Badly done, T&T.
Ian McShane as Blackbeard was appropriately menacing, but I agree with
geekmama's opinion that he was rather one-dimensional as a villain, in contrast to Barbossa, Davy Jones and even Beckett. We never learn what motivates him, it seemed like he was evil simply for evil's sake, which was a pity, because I don't doubt that McShane could have done much more with the role if there had been room for it, he did wonders with Al Swearengen in Deadwood after all. Side notes: Is it required of magicked ships to have sails full of holes? And zombies? Why?
Angelica, then. Jack was never my focus when I shipped Jack/Elizabeth, it was Elizabeth. So to be able to enjoy Jack/Angelica, I would have needed to be able to shift my focus to Angelica, and that hinged on me liking her. Which I didn't. It was probably in part because I don't like Penélope Cruz, but the character as such didn't click for me either. I realise that she was supposed to be this tough, fiery pirate, a match for Jack, but I didn't feel it. And I couldn't quite understand, considering Blackbeard's behaviour, why she was willing to sacrifice everything for him.
The mermaids were fierce and deadly and awesome! Unfortunately I didn't think that the girl who played Syrena managed to convey any of that properly, so there was a lot of unused potential there. I liked Philip okay and it should have been fascinating, a mermaid and a missionary finding each other, but their story was woefully underdeveloped and happened too fast. The only time I found it as compelling as I wanted to was in the final scene between them. But I would like to read Syrena/Philip stories, preferably from her POV, so I'll be on the lookout for that!