you might consider lowering the fillfactor a bit. It will consume more space, but it will make updates and inserts faster.
http://www.postgresql.org/docs/8.4/interactive/sql-createtable.html : fillfactor (integer) The fillfactor for a table is a percentage between 10 and 100. 100 (complete packing) is the default. When a smaller fillfactor is specified, INSERT operations pack table pages only to the indicated percentage; the remaining space on each page is reserved for updating rows on that page. This gives UPDATE a chance to place the updated copy of a row on the same page as the original, which is more efficient than placing it on a different page. For a table whose entries are never updated, complete packing is the best choice, but in heavily updated tables smaller fillfactors are appropriate. This parameter cannot be set for TOAST tables. -- "Patriotism is the conviction that your country is superior to all others because you were born in it." -- George Bernard Shaw
