Nathan
Not strictly accurate. Pix v6.x and before did not support outbound acls on an interface. However Pix v7.x and onwards does support outbound acls so both the ASA and Pix (v7.x onwards) support both outbound and inbound acls.
When to use outbound acls really depends on your requirements. Most times you can use inbound acls but outbound can be useful in certain situations.
Jon