Is it clever to put the AGND ground pour ONLY on the bottom layer and the DGND ground pour ONLY on top layer?
you'll have a lot of capacitive coupling between the two planes - you're better off putting all the analog in one clean place, with a single ground plane, connected to the rest of the world at just one point (so digital ground currents don't decide to take a short cut across it), and a carefully decoupled single power supply point