First, right off the bat in what seemed to be a throwaway line, we found out the answer to a huge question that we've been asking for decades.
YES, apparently Timelords CAN change gender when they regenerate!
What could that mean for future incarnations of Doctors, Masters, etc?
Second--Rory's dying. Okay, so he didn't ACTUALLY die in this episode...but they did make sure to show him dead, whether it was real or not.
I don't think it's coincidence that in every single episode this season, Rory has died. Could it be that he's actually dead in another dimension/timeline? Or could it mean that he's SUPPOSED to be dead in THIS timeline (maybe he was supposed to have actually stayed dead when he was shot by the silurian?) and Amy's bringing him back messed things up?
Third--Again, Rory mentions his being a nurse. Again, he's done this in every episode of the season so far. Again, I don't think this is coincidence! This is going to mean something in future episodes! Mark my words! ;)
Fourth-Did anyone catch Idris/TARDIS saying, "I love you" to the Doctor as she "died". Broke my heart! :(
Fifth--"The only water in the forest is the river". Obviously, this is a reference to River Song and another thing that will come to pass in future episodes.
But what forest? The forest in Byzantuim, where the weeping angels were? Or the "forest" in the library, where River met her demise? Is it possible that River will somehow be "reborn" (Amy's pregnancy, perhaps??) or "downloaded" into a new body as the TARDIS was?
I really, really loved this episode. It was hilariously touching and devastatingly sad. I think it's my second favourite Matt Smith episode, just below Vincent and the Doctor!