9.0rc1 ?
You know that the stable 9.0 has been out for quite a while now.
Its not going to affect the delete speed in any way, but I would
generally advice you to upgrade it to the lates 9.0.x
As for the delete it self, check if you have indices on the tables
that refer the main table on the referred column. Often times that's
the issue.
Other thing is , number of triggers on the other tables.
--
GJ