The A, B, Select, Start buttons and the control pad remind the Gameboy Color disposition completely.
You have an additional light ON/OFF button right on top (no regulation of the light intensity, seems like we should start on making a dimmer chip for the unit... it just confirms to all of us we definitely don't live in a perfect world)
The L and R buttons have changed completely, compared to the flat design on the first GBA, these toggles are now very tiny and in square shape.