I absolutely love the video chip of the Ataris. The display list approach is nothing short of brilliant, allowing multiple display modes on a single frame.
To be fair, that was also possible on some other 8-bit home computers of the time, but required the CPU to get involved (with tricky timing code to write the hardware registers at the right time). The 8-bit Atari's display list coprocessor is basically the daddy of the Amiga's Copper :)