Just thought I would relate this, since it is tangible evidence of what is reported in the manuals under WAL tweaking - hope someone finds it useful.
My performance was 76 seconds before tuning versus 7 seconds after tuning.
TASK: Create and populate a table with 30 columns, adding 8,000 rows METHOD: Only INSERT statements (accessed via php which does not allow COPY statements)
SYSTEM: Using an 8.3 install (I know, I know)
WAL CONFIG: changed the default setting of "synchronous_commit = off" to "synchronous_commit = on"
-- Robert W. Burgholzer 'Making the simple complicated is commonplace; making the complicated simple, awesomely simple, that's creativity.' - Charles Mingus