Just to second the praise for the postgres mailing lists - my firstexperiences with it (in the past few weeks) have been amazing - quick replies from Tom Lane that had me in the right direction.
"The right direction" being the key - opensource guys love to help out - but they are not paid to hold your hand.
Some clients need their hand holding - so either you plan to do that yourself, or tell them to buy Oracle and hire a dba ;)
On Oracle vs. Postgres - I just like developing in Oracle, for some reason it's api(s) "feel" nicer. Having said that, I use postgres for all my projects now, because for the very small amount of less niceness - it's a heck of a lot cheaper! It's less tuneable, which is both good and bad.
(It's also worth noting that I use Apple Mac's, so filter my tastes accordingly!)
