For me Lion DP3 has about he same stability as DP2 in terms of overall usability. It did fix a bug in Mission Control I was having where the active desktop in the previews at the top of MC was not showing anything but the default textured grey background (no apps, etc.). I was also having a beach balling issue with Safari, but that turned out to be Tab Expose's fault. Animations in Launchpad are definitely smoother. The old trick used to remove apps from Launchpad does not work anymore though unfortunately. Some apps show the "X" to remove them, but not all do.