TH:
Ambient Occlusion is a 'Lighting Model' (found on the 'Lighting' tab of the Atmosphere Editor), just like GI and GR. So i guess you'd say it's global (not per-object or per-material).

Could you define "self-shadowing"? Any material (in Material Editor) can cast shadows or not and receive shadows or not, or be rendered as a shadow only. If you set a material to receive shadows, this includes from itself (no way i know to disable self shadows only).

The main thing i noticed in V6 for shadows is the cool shadow softness and custom shadow softness features in the Light & Shadow Editor. These are really good for getting rid of artifacts ("grain") from the complex process of calculating smooth shadow edges - and with fast rendering  too. No need for Object Antialiasing or Texture Antialiasing for soft shadows now (but you may still need OAA or TAA for other reasons).