The Post subclasses have fields that are actually available from facebook for generic Post types.
For example, any post type may have a Page representing a Place:
CheckinPost does have getPlace(), but other Post types are allowed to have a location.
PhotoPost has a mapping for object_id to getPhotoId(), but other post types may have an object_id that corresponds to a photo object.
is "type": "status",
but has "place":
I believe it would be useful to collapse all the Post subclasses into Post itself.
probably worth a shiny new bug: looks like the Post with_tags element is not picked up by any Post field.
Likewise, the "tags" element is not documented in the Facebook apis on Post. I suspect you are using the Photo tag logic, rather than a new Mixin thing for the element tag.