In the CRUD/update section ( http://docs.mongodb.org/manual/applications/update/ ) , I think the "update by doc" and "update by modifiers" alternative should be more explicit for beginners.

It is also difficult, even for a seasoned user to find a link to the page listing the $modifiers ( http://docs.mongodb.org/manual/reference/operators/#update-operators ). I think this is important enough to appear as a see also very close to the top of the "Update" part. I guess that would come naturally if the first suggestion (explicit discussion of the modifiers) is followed.