group by not returning sorted rows

I have a query:



select cities.name as city, buildings.name as building, pagename, log_date , sum(exhibition_count) as tot 
from logrecords join cities on (logrecords.city=cities.num) join buildings on (logrecords.building=buildings.num) 
where     advertiser = 'Nielsens' and log_date >= '01/01/2004' and log_date <= '01/31/2004' 
group by cities.name, buildings.name,pagename,log_date ;

I have migrated a database from a redhat 7.3 box running 
[bhughes@compaq3 reports]$ rpm -q postgresql
postgresql-7.2.3-5.73


To a redhat 9 box running :
[bhughes@compaq2 reports]$ rpm -q postgresql
postgresql-7.4.2-1PGDG

and the rows resulting from the query are no longer sorted by log date. 
Is this a change since 7.2x?

I can achieve the results I need by adding an order by clause identical
to the group by but this seems counter intuitive since the rows have to
be ordered anyway.

Any tips appreciated.

Bret