In a nutshell, here's what we found out about River Song in tonight's episode:

The Silence spent years and all of the considerable brain-wiping powers brainwashing River Song to kill the Doctor, but instead of killing him, she fell in love with him. As she puts it, "It was such a basic mistake, wasn't it, Madame Kovarian? Take a child, raise her into a perfect psychopath, introduce her to the Doctor... Who else was I going to fall in love with?" So her love for the Doctor is actually a reflection of her broken psyche.

And yet, even though River technically is the one who "kills" the Doctor, it's actually the suit that does all the work. She says, "The suit's in control. I can't stop it." Which makes you wonder why they didn't just send an empty suit after the Doctor in the first place — except that I think it has to do with River having special timey-wimey powers. (More on that in a minute.) River does manage to take control over the suit and discharge the weapons systems, leaving it powerless — and creating a weird alternate universe where all of time is happening at once, and the universe is threatened with disintegration.

River loves the Doctor so much, she's willing to sacrifice the entire universe for him — which is the opposite of what the Doctor stands for. In fact, it's a weird kind of love, that is willing to destroy the loved one's legacy. (Leaving aside the fact that if the universe dies, River and the Doctor won't have any place to share their love in.) The scene where River says, "You are loved so much by so many and so much, and by no-one more than me" is lovely — except for that line, which is either hideously overwritten or overacted, maybe both.

So in order to get River to restart the universe and set things right, the Doctor has to marry her — you'll notice the Doctor never says he loves her, and he makes fun of her for saying she loves him. Soon afterwards, the Doctor tells River, "I don't want to marry you." And then, right before he does marry her, he tells her, "You embarrass me," and he genuinely seems to be full of loathing for her in that moment. During the actual quickie wedding ceremony, River asks, "What am I doing?" and the Doctor replies, "as you're told." Awwww... so romantic. Finally, the Doctor tells her, "Now you're the woman who marries me," as if she's won the jackpot. (Plus of course, the wedding happened in a bubble universe that was erased.)

So what does River get for marrying the Doctor and taking the fall for his fake murder? She gets locked up in Stormcage for almost the rest of her life — apparently she gets out, in time to die in "Forest of the Dead." She's not only given up all her regenerations to bring the Doctor to life and given her final life to save him, she's also agreed to be locked away in prison and reviled as one of history's greatest criminals, just to help the Doctor lower his profile a bit. (Because even if the Doctor had to appear to die by that lakeside to safeguard the "fixed point in time," there's no law that says he couldn't show up at River's trial and say "Hello, it's me. Actually didn't die. Thanks.")

As a consolation prize, River gets to leave her cell every night and go traveling with the Doctor, in a series of adventures that we'll never get to see — since apparently, they all happened in the gap between "The God Complex" and "Closing Time." (Remember, in "The Impossible Astronaut," the Doctor who meets River in Utah has already lived through all the adventures in her magic diary.)

I'm sure we'll see River Song again, but I'm also sure that her story is basically played out. We've seen her birth and her death, and we've apparently gotten answers to all the major questions about her. And honestly, her character has lost most of its appeal at this point — she's now the psychopath who blackmailed the Doctor into marrying her by holding the universe for ransom, and then took the fall for him. Once she was locked up for a crime that the Doctor basically framed her for, he took pity on her and led her on some fun adventures.