I just added a feature which wraps all of the posts in a day in a div (class "calendaryday") and sticks as the first thing in it the day in an H2 tag (e.g. Wednesday, April 21, 2004).
That is, powerblogs can now immitate either Blogger or Movable Type in grouping the posts of a given day together and putting a heading indicating which day they're in. It's a Blog Preference which defaults to off.