The other problem actually existed in 19 as well; if you resize a window to be larger, you might get a flash of black or garbage until the repaint driver wakes up and redraws the window. This is merely a nuisance really, but it looks ugly, so I'm thinking of how to force the resize event to invalidate immediately.
Intel 17.0.2 users affected by the freeze bug, recently confirmed by Claudio, may wish to watch issue 209. Again, no ETA -- it's unsupported, remember?
More this weekend when I'm back from my business trip.