PostgreSQL index quesiton for version < 7.4

Hi,

In the HISTORY file for PostgreSQL 7.4, it says:

Make free space map efficiently reuse empty index pages, and other
free space management improvements.

In previous releases, B-tree index pages that were left empty
because of deleted rows could only be reused by rows with index
values similar to the rows originally indexed on that page. In
7.4, "VACUUM" records empty index pages and allows them to be
reused for any future index rows.

I have a table that is indexed on a sequence field that always increments.
As new rows are inserted, they are given the next ID in the sequence.
Oldre rows are deleted periodically.

For PG < 7.4, does the index grow without the free space being reclaimed?
Would this affect performance substantially? I have had reports from
customers who said our applications speed improved tremendously after
a database dump/drop/recreate/restore recycle. (We do run VACUUM ANALYZE
regularly, so it's not the lack of that that would cause it to slow down.)

Will PG 7.4 improve the performance if this is indeed a problem?

Regards,

David.