autovacuum questions

Hello Gurus,
I'm new to PG , running PG 8.3 on Linux and reading trough docs  is
mentioned that in PG vers 8.3  an AUTO vacuum process   has been
implemented which will run
full vacuum  on  all user and system tables + analyze  and there is  NO
need fro DBA  to schedule a crontab job to run this  maintenance jobs .
If this is true , here are my questions :
Would like to know from your experience is this automated process
sufficient and reliable in a warehouse database , can I rely only  on
this  internal  process ?
How can I see when the job has been run or completed by PG ?
I have configure track_count=true, what values should I go for
autovacuum_naptime  from your experience?

Isabella