Ok, to be honest I really rather like River Song. I even have an action figure of her. While a lot of people never got over how smug she was in her first few appearances, I gave her a chance based on the very clear statement that we came in at the end of her story as opposed to the beginning. When we meet her in the library, it's mere hours before she dies, sacrificing herself to save the Tenth Doctor and... well, everyone who survived initial contact with the Vashta Nerada. Since then, we've been working our way backwards, forwards, and sideways in her timeline, meeting her as a psychotic programmed killer, a helpless child, a rebellious teenager, a master con artist, and cat burglar and if you piece it together in HER chronological order, she's gotten a startling amount of character development, finally justifying the cocky assuredness of Silence in the Library.
When we met a ghost of her near the end of Eleven's run, I was sure we'd seen the last of her. The fact that she was literally appearing from beyond the grave, or so she claimed, seemed to tell of a final appearance, but she's back again.
This.. isn't a terribly good story. But then, it's a Christmas special, and we all know how to handle Christmas specials. They're completely bonkers. The overarching events may be in canon to the rest of the series, but the details are clearly hyperbole. Events like the Satsuma Incident of the Sycorax Invasion or the Great Sleigh Ride of the Twelfth are surely exaggerated versions of what really happened, possibly told by an as-of-yet unmet Doctor to an unseen companion. The story here is no different, with what amounts to a cross-time heist caper filled with ridiculous moments that serve less to tell a convincing story and more to set up a proper farewell to River.
The running joke of River not recognizing the Doctor in his twelfth incarnation, right down to stealing the TARDIS with him present, was great fun. Especially with his hilariously over-the-top reaction to the TARDIS being bigger on the inside, complete with a Danny Elfman-esque backing score. The personality of the villain Hydroflax's robot body was entertaining as well, even if Hydroflax himself was rather cookie-cutter villain. River is fun here, too, a different River than we're used to. More cynical and ruthless, or at least appearing to be.
But really, the reason we're here is the ending. As the Doctor uses the jewel River stole to fund the building of the restaurant he always promised to take her to, makes reservations for four years in advance, and changes into a proper suit for her all in the time it takes her to come to after their back-and-forth rescuing of each other. This really does feel like closing the book on River Song, especially coming so closely on the heels of closing the book on Clara Oswald. River gets a proper goodbye, and one last night with the Doctor, on a planet where the nights are twenty-four years long. Aside from his duty of care for Clara, this is truly the first time we see Twelve soften, even become romantic, as River gets what she's always wanted. To be with her husband, their timelines more in sync with each other than ever before, before seeing him one last time as a young man, his first meeting with her and her last.
Goodbye, River. You were controversial. You were cocky. You were scared and scary and dangerous and I had a lot of fun watching it all, even if not everyone did. You got what every good character deserves: A proper send-off. And during a Christmas special, too, with every excuse to be as bonkers as possible. Just like you.