While running some astronomy apps (Sky Chart, Lunar Atlas, Sofortbild for remote camera control), and just for fun leaving Aperture, Excel, Powerpoint, Airmail, Notes, iCal, Wunderlist and iMessage open - I finally managed to get 16GB virtual used on my 8GB real MBP, still no slowdowns, pauses, beachballs etc and no discernable delays in the UI when switching etc....very impressed!