Empty cells appear last in sort regardless of whether ascending or descending
sort is selected.

From a practical point of view there are instances where users would want to
sort nulls first. e.g. sheet with columns 'date created', 'date resolved',
'action requested'

If user wishes to keep unresolved requests at top of sheet by ordering on 'date
resolved'/descending+'date created' the desired result isn't achieved. All the
unresolved (null cell) issues sort to the bottom of the list. Depending on the
length of the list they disappear off the bottom of the screen.

A workaround is non-intuitive step of putting a space in 'date resolved' column.
That makes the worksheet difficult to maintain because it can't be determined if
a cell has space entered or is null just by looking at it. Plus user must
remember to put spaces in otherwise empty cells to make sort occur in desired
fashion.

The enhancement requested is that an option to sort nulls before or after other
values be provided. 

There has already been a conscious decision made to have nulls appear at the end
of a sorted list, regardless of sort order. The effect is that nulls are, in
effect, being sorted but _always_ being forced to the end of the list. 

How about providing some control over that behavior so that nulls appearing at
the beginning or end of the sorted list is user selectable? Hopefully it can be
seen from the scenario described above that there are practical user focused
reasons to provide this behavior.