I became the proud owner of one SB-900 to add to my two SB-600s mid November. I got a chance to use everything for our family Christmas photos.
SB-600 behind them shooting up at a white sheet, SB-900 in a 60 inch phototek softlighter camera right and high (awesome big light with quality similar to an Octa for much less $$$), and one SB-600 low and camera left through an umbrella for fill.
Cool thread!