Positive feedback on Ebay has become a form of extortion and Dizzy makes a good point. You are not doing anything wrong by holding off on the feedback until you now the item arrived and the buyer is happy, there are plenty of freaks out there
Buy it now is pretty effective if you know what an item is worth. There are alot of people who don't want to watch an auction for 7 days, waiting for it to end. Plus some folks put ridiculously low BINs on items and you can get some real steals.