We don't know when she adopts the name 'River'. As a baby, she hasn't seen the prayer leaf with that name on it yet. She could well be raised as Melody, but then take the name River for another reason.

Or perhaps she only drops the name Melody when she stops being a weapon.

I liked Amy at first, but I think that was more to do with little Amelia's story. Gradually Amy become more irritating, while Rory became more entertaining. I did like the 'full Tardis' in the opening 2 parter, Canton, River, Amy, Rory and the Doctor made a good team. I'll be surprised if the Ponds are around for series 7. I've always thought the most plausible way for them to be written out would be if they wanted to start a family.