No more grey flashing while resizing. Explorer and every other window flashed to plain grey on each step of a resize: the X server wiped the window to its background colour before the repaint. Windows now carry no server-side background, keep their contents in place during the resize, and repaint on the spot. The window manager's frames get the same treatment.
Update with the usual command; a running desktop restarts in place. Programs already open keep the old behaviour until reopened.
curl -sL jacktulli.github.io/w2k | sh